title: Mexican Americans

text: As the United States' borders expanded, the United States Census Bureau changed its racial classification methods for Mexican Americans under United States jurisdiction. The Bureau's classification system has evolved significantly from its inception:


title: Mexican Americans

text: For certain purposes, respondents who wrote in "Chicano" or "Mexican" (or indeed, almost all Latino origin groups) in the "Some other race" category were automatically re-classified into the "White race" group.


title: Mexican Americans

text: In some cases, legal classification of White racial status has made it difficult for Mexican-American rights activists to prove minority discrimination. In the case "Hernandez v. Texas" (1954), civil rights lawyers for the appellant, named Pedro Hernandez, were confronted with a paradox: because Mexican Americans were classified as White by the federal government and not as a separate race in the census, lower courts held that they were not being denied equal protection by being tried by juries that excluded Mexican Americans by practice. The lower court ruled there was no violation of the Fourteenth Amendment by excluding people with Mexican ancestry among the juries. Attorneys for the state of Texas and judges in the state courts contended that the amendment referred only to racial, not "nationality," groups. Thus, since Mexican Americans were tried by juries composed of their racial group—whites—their constitutional rights were not violated. The US Supreme Court ruling in "Hernandez v. Texas" case held that "nationality" groups could be protected under the Fourteenth Amendment, and it became a landmark in the civil rights history of the United States.


title: Mexican Americans

text: While Mexican Americans served in all-White units during World War II, many Mexican–American veterans continued to face discrimination when they arrived home; they created the G.I. Forum to work for equal treatment.


title: Mexican Americans

text: In times and places in the United States where Mexicans were classified as White, they were permitted by law to intermarry with what today are termed "non-Latino whites." Social customs typically approved of such marriages only if the Mexican partner was not of visible Indigenous ancestry.


title: Mexican Americans

text: Legally, Mexican Americans could vote and hold elected office; however, in many states electoral practices discriminated against them, especially as a language minority. After they created political organizations such as the League of United Latin America Citizens and the G.I. Forum, Mexican Americans began to exert more political influence and gain elective office. Edward Roybal's election to the Los Angeles City Council in 1949 and to Congress in 1962 also represented this rising Mexican-American political power.


title: Mexican Americans

text: In the late 1960s the founding of the Crusade for Justice in Denver and the land grant movement in New Mexico in 1967 set the bases for what would become known as Chicano (Mexican American) nationalism. The 1968 Los Angeles, California school walkouts expressed Mexican-American demands to end "de facto" ethnic segregation (also based on residential patterns), increase graduation rates, and reinstate a teacher fired for supporting student political organizing. A notable event in the Chicano movement was the 1972 Convention of La Raza Unida (United People) Party, which organized with the goal of creating a third party to give Chicanos political power in the United States.


title: Mexican Americans

text: In the past, Mexicans were legally considered "White" because either they were accepted as being of Spanish ancestry, or because of early treaty obligations to Spaniards and Mexicans that conferred citizenship status to Mexican peoples before the American Civil War. Numerous slave states bordered Mexican territory at a time when 'whiteness' was nearly a prerequisite for US citizenship in those states.


title: Mexican Americans

text: Although Mexican Americans were legally classified as "white" in terms of official federal policy, socially they were seen as "too Indian" to be treated as such. Many organizations, businesses, and homeowners associations and local legal systems had official policies in the early 20th century to exclude Mexican Americans in a racially discriminatory way. Throughout the Southwest, discrimination in wages was institutionalized in "White wages" versus lower "Mexican wages" for the same job classifications. For Mexican Americans, opportunities for employment were largely limited to guest worker programs.


title: Mexican Americans

text: The "bracero" program, begun in 1942 during World War II, when many United States men were drafted for war, allowed Mexicans temporary entry into the United States as migrant workers at farms throughout California and the Southwest. This program continued until 1964.


title: Mexican Americans

text: A number of western states passed anti-miscegenation laws, directed chiefly at Chinese and Japanese. As Mexican Americans were then classified as "White" by the census, they could not legally marry African or Asian Americans (See "Perez v. Sharp"). According to historian Neil Foley in his book "The White Scourge: Mexicans, Blacks, and Poor Whites in Texas Cotton Culture", Mexicans and Mexican-Americans in Texas did marry non-Whites, typically without reprisal.


title: Mexican Americans

text: While of racial segregation and discrimination against both Mexican American and African American minorities were subject to segregation and racial discrimination, they were treated differently. There were legal racial demarcations between Whites and blacks in a state like Texas, whereas the line between Whites and Mexican Americans was not legally defined. Mexican Americans could attend White schools and colleges (which were racially segregated against blacks), mix socially with Whites and, marry Whites. These choices were prohibited to African Americans under state laws. Racial segregation operated separately from economic class and was rarely as rigid for Mexican Americans as it was for African Americans. For instance, even when some African Americans in Texas enjoyed higher economic status than Mexican Americans (or Whites) in an area, they were still segregated by law.


title: Mexican Americans

text: Mexican Americans have influenced American cuisine, burritos, enchiladas, guacamole, nachos, tacos, tamales, and tortillas, are regular in American vernacular. The cuisines of New Mexican and Tex-Mex are native to the cuisine of the Southwestern United States, and Mexican cuisine has influenced Californian cuisine.


title: Mexican Americans

text: The popular radio format Regional Mexican includes Mexican styles of music; Norteño, ranchera, Conjunto, Son Jarocho, and mariachi. It also includes the indigenous and Mexican American music styles of the New Mexico music, Tejano music, Chicano rock, and Chicano rap, which originate in the United States.


title: Mexican Americans

text: Since the 1960s, Mexican immigrants have met a significant portion of the demand for cheap labor in the United States. Fear of deportation makes them highly vulnerable to exploitation by employers. Many employers, however, have developed a "don't ask, don't tell" attitude toward hiring undocumented Mexican nationals. In May 2006, hundreds of thousands of undocumented immigrants, Mexicans and other nationalities, walked out of their jobs across the country in protest to support immigration reform (many in hopes of a path to citizenship similar to the Immigration Reform and Control Act of 1986 signed into law by President Ronald Reagan, which granted citizenship to Mexican nationals living and working without documentation in the US). Governmentalities have been the result of unequal relations with its northern neighbors versus a response to more locally driven needs.


title: Mexican Americans

text: US politicians cited numbers as high as 20 million undocumented immigrants in the United States without providing statistical proof.


title: Mexican Americans

text: Even legal immigrants to the United States, both from Mexico and elsewhere, have spoken out against illegal immigration. However, according to a survey conducted by the Pew Research Center in June 2007, 63% of Americans would support an immigration policy that would put undocumented immigrants on a path to citizenship if they "pass background checks, pay fines and have jobs, learn English", while 30% would oppose such a plan. The survey also found that if this program was instead labeled "amnesty", 54% would support it, while 39% would oppose.


title: Mexican Americans

text: Alan Greenspan, former Chairman of the Federal Reserve, has said that the growth of the working-age population is a large factor in keeping the economy growing and that immigration can be used to grow that population. According to Greenspan, by 2030, the growth of the US workforce will slow from 1 percent to 1/2 percent, while the percentage of the population over 65 years will rise from 13 percent to perhaps 20 percent. Greenspan has also stated that the current immigration problem could be solved with a "stroke of the pen", referring to the Comprehensive Immigration Reform Act of 2007 which would have strengthened border security, created a guest worker program, and put undocumented immigrants currently residing in the US on a path to citizenship if they met certain conditions.


title: Mexican Americans

text: According to data published by the Bank of Mexico, Mexicans in the United States sent $24.7 billion in remittances to Mexico in 2015.


title: Mexican Americans

text: Throughout US history, Mexican Americans have endured various types of negative stereotypes which have long circulated in media and popular culture. Mexican Americans have also faced discrimination based on ethnicity, race, culture, poverty, and use of the Spanish language.


title: Mexican Americans

text: Mexicans faced racially segregated schooling in a number of Western states during the Depression era. In Wyoming, the segregation of Mexican children—regardless of US citizenship—mirrored the South's Jim Crow laws. The segregation of Mexicans also occurred in California and in neighboring Colorado, Montana, and Nebraska.


title: Mexican Americans

text: Since the majority of undocumented immigrants in the US have traditionally been from Latin America, the Mexican American community has been the subject of widespread immigration raids. During The Great Depression, the United States government sponsored a Mexican Repatriation program which was intended to encourage people to voluntarily move to Mexico, but thousands were deported against their will. During the 1930s, between 355 000 and 1 million individuals were repatriated or deported to Mexico, approximately 40 to 60 percent of which were actually United States citizens - overwhelmingly children. Voluntary repatriation was far more common than formal deportation. In the post-war era, the Justice Department launched Operation Wetback.


title: Mexican Americans

text: During World War II, more than 300,000 Mexican Americans served in the US armed forces. Mexican Americans were generally integrated into regular military units; however, many Mexican–American War veterans were discriminated against and even denied medical services by the United States Department of Veterans Affairs when they arrived home. In 1948, war veteran Hector P. Garcia founded the American GI Forum to address the concerns of Mexican American veterans who were being discriminated against. The AGIF's first campaign was on the behalf of Felix Longoria, a Mexican American private who was killed in the Philippines while in the line of duty. Upon the return of his body to his hometown of Three Rivers, Texas, he was denied funeral services because of his nationality.


title: Mexican Americans

text: In the 1948 case of "Perez v. Sharp", the Supreme Court of California recognized that the ban on interracial marriage violated the Fourteenth Amendment of the Federal Constitution from 1868. The case involved Andrea Perez, a Mexican-American woman listed as White, and Sylvester Davis, an African American man.


title: Mexican Americans

text: In 2006, "Time" magazine reported that the number of hate groups in the United States increased by 33% since 2000, with illegal immigration being used as a foundation for recruitment. According to the 2011 Federal Bureau of Investigation (FBI) Hate Crimes Statistics Report, 56.9% of the 939 victims of crimes motivated by a bias toward the victims’ ethnicity or national origin were directed at Latinos. In California, the state with the largest Mexican American population, the number of hate crimes committed against Latinos almost doubled from 2003 to 2007. In 2011, hate crimes against Latinos declined 31% in the United States and 43% in California.


title: Mexican Americans

text: There have been increases in average personal and household incomes for Mexican Americans in the 21st century. US-born Americans of Mexican heritage earn more and are represented more in the middle and upper-class segments more than most recently arriving Mexican immigrants.


title: Mexican Americans

text: Most immigrants from Mexico, as elsewhere, come from the lower classes and from families generationally employed in lower skilled jobs. They also are most likely from rural areas. Thus, many new Mexican immigrants are not skilled in white collar professions. Recently, some professionals from Mexico have been migrating, but to make the transition from one country to another involves re-training and re-adjusting to conform to US laws —i.e. professional licensing is required. Millions crossed into the United States to find work that would help them survive as well as sustain their families in Mexico.


title: Mexican Americans

text: According to James P. Smith, the children and grandchildren of Latino immigrants tend to lessen educational and income gaps with White American. Immigrant Latino men earn about half of what whites make, while second generation US-born Latinos make about 78 percent of the salaries of their white counterparts and by the third generation US-born Latinos make on average identical wages to their US-born white counterparts. However, the number of Mexican American professionals have been growing in size since 2010.


title: Mexican Americans

text: The Mexican median household income was a mere $37,390 compared to that of $49,487 and $54,656 for immigrants and native-born populations respectively. This pushed 28% of Mexican families to live in poverty, to put that in perspective the rest of the immigrants where at 18% and native-born families 10%.


title: Mexican Americans

text: Huntington (2005) argues that the sheer number, concentration, linguistic homogeneity, and other characteristics of Latin American immigrants will erode the dominance of English as a nationally unifying language, weaken the country's dominant cultural values, and promote ethnic allegiances over a primary identification as an American. Testing these hypotheses with data from the US Census and national and Los Angeles opinion surveys, Citrin et al. (2007) show that Latinos generally acquire English and lose Spanish rapidly beginning with the second generation, and appear to be no more or less religious or committed to the work ethic than native-born non-Mexican American whites. However, the children and grandchildren of Mexican immigrants were able to make close ties with their extended families in Mexico, since United States shares a 2,000 mile border with Mexico. Many had the opportunity to visit Mexico on a relatively frequent basis. As a result, many Mexicans were able to maintain a strong Mexican culture, language, and relationship with others.


title: Mexican Americans

text: South et al. (2005) examine Latino spatial assimilation and inter-neighborhood geographic mobility. Their longitudinal analysis of seven hundred Mexican, Puerto Rican, and Cuban immigrants followed from 1990 to 1995 finds broad support for hypotheses derived from the classical account of assimilation into American society. High income, English-language use, and embeddedness in American social contexts increased Latin American immigrants' geographic mobility into multi-ethnic neighborhoods. US citizenship and years spent in the United States were positively associated with geographic mobility into different neighborhoods while co-ethnic contact and prior experiences of ethnic discrimination decreased the likelihood that Latino immigrants would move from their original neighborhoods and into non-Latino white census tracts.


title: Mexican Americans

text: According to 2000 census data, US-born ethnic Mexicans have a high degree of intermarriage with non-Latino whites. Based on a sample size of 38,911 US-born Mexican husbands and 43,527 US-born Mexican wives:


title: Mexican Americans

text: In addition, based on 2000 data, there is a significant amount of ethnic absorption of ethnic Mexicans into the mainstream population with 16% of the children of mixed marriages not being identified in the census as Mexican.


title: Mexican Americans

text: A study done by the National Research Council (US) Panel on Latinos in the United States published in 2006 looked at not only marriages, but also non-marriage unions. It found that since at least 1980, marriage for females across all Latino ethnic groups, including Mexican Americans, has been in a steady decline. In addition, the percentage of births to unmarried mothers increased for females of Mexican descent from 20.3% in 1980 to 40.8% in 2000, more than doubling in that time frame. The study also found that for females of all Latino ethnicities, including Mexican origin, "considerably fewer births to unmarried Latino mothers involve partnerships with non-Latino white males than is the case for married Latino mothers. Second, births outside marriage are more likely to involve a non-Latino black father than births within marriage." Additionally, "Unions among partners from different Latino origins or between Latinos and non-Latino blacks are considerably more evident in cohabitation and parenthood than they are in marriage. In particular, unions between Latinos and non-Latino blacks are prominent in parenthood, especially non-marital births." Furthermore, for 29.7% of unmarried births to native-born females of Mexican origin and 40% of unmarried births to females of "Other Latino" origin, which may include Mexican American, information on the father's ethnicity was missing. The study was supported by the US Census Bureau, amongst other sources.


title: Mexican Americans

text: Studies have shown that the segregation among Mexican Americans and Mexican immigrants seems to be declining. One study from 1984 found that Mexican American applicants were offered the same housing terms and conditions as non-Latino white Americans. They were asked to provide the same information (regarding employment, income, credit checks, etc.) and asked to meet the same general qualifications of their non-Latino white peers. In this same study, it was found that Mexican Americans were more likely than non-Latino white Americans to be asked to pay a security deposit or application fee and Mexican American applicants were also more likely to be placed onto a waiting list than non-Latino white applicants.


title: Mexican Americans

text: The Battle of Chavez Ravine has several meanings, but often refers to controversy surrounding government acquisition of land largely owned by Mexican Americans in Los Angeles' Chavez Ravine over approximately ten years (1951–1961). The eventual result was the removal of the entire population of Chavez Ravine from land on which Dodger Stadium was later constructed. The great majority of the Chavez Ravine land was acquired to make way for proposed public housing. The public housing plan that had been advanced as politically "progressive" and had resulted in the removal of the Mexican American landowners of Chavez Ravine, was abandoned after passage of a public referendum prohibiting the original housing proposal and election of a conservative Los Angeles mayor opposed to public housing. Years later, the land acquired by the government in Chavez Ravine was dedicated by the city of Los Angeles as the site of what is now Dodger Stadium.


title: Mexican Americans

text: When comparing the contemporary segregation of Mexican Americans to that of Black Americans, some scholars claim that "Latino segregation is less severe and fundamentally different from Black residential segregation." suggesting that the segregation faced by Latinos is more likely to be due to factors such as lower socioeconomic status and immigration while the segregation of African Americans is more likely to be due to larger issues of the history of racism in the US.


title: Mexican Americans

text: Legally, Mexican Americans could vote and hold elected office, however, it was not until the creation of organizations such as the League of United Latin America Citizens and the G.I. Forum that Mexican Americans began to achieve political influence. Edward Roybal's election to the Los Angeles City Council in 1949 and then to Congress in 1962 also represented this rising Mexican American political power. In the late 1960s the founding of the Crusade for Justice in Denver in and the land grant movement in New Mexico in 1967 set the bases for what would become the Chicano (Mexican American) nationalism. The 1968 Los Angeles school walkouts expressed Mexican American demands to end segregation, increase graduation rates, and reinstate a teacher fired for supporting student organizing. A notable event in the Chicano movement was the 1972 Convention of La Raza Unida (United People) Party, which organized with the goal of creating a third party that would give Chicanos political power in the United States.


title: Mexican Americans

text: In the past, Mexicans were legally considered "White" because either they were considered to be of full Spanish heritage, or because of early treaty obligations to Spaniards and Mexicans that conferred citizenship status to Mexican peoples at a time when whiteness was a prerequisite for US citizenship. Although Mexican Americans were legally classified as "White" in terms of official federal policy, many organizations, businesses, and homeowners associations and local legal systems had official policies to exclude Mexican Americans. Throughout the southwest discrimination in wages were institutionalized in "white wages" versus lower "Mexican wages" for the same job classifications. For Mexican Americans, opportunities for employment were largely limited to guest worker programs. The bracero program, which began in 1942 and officially ended in 1964, allowed them temporary entry into the United States as migrant workers in farms throughout California and the Southwest.


title: Mexican Americans

text: Mexican Americans legally classified as "White", following anti-miscegenation laws in most western states until the 1960s, could not legally marry African or Asian Americans (See "Perez v. Sharp"). However, most were not socially considered white, and therefore, according to Historian Neil Foley in the book "The White Scourge: Mexicans, Blacks, and Poor Whites in Texas Cotton Culture", Mexicans and Mexican-Americans did marry non-whites typically without reprisal.


title: Mexican Americans

text: Despite the similarities between Mexican American and African American patterns of segregation, there were important differences. The racial demarcations between whites and blacks in a state like Texas were inviolable, whereas those between whites and Mexican Americans were not. It was possible for Mexican Americans to attend white schools and colleges, mix socially with whites and, on occasion, marry whites: all of these things were impossible for African Americans, largely due to the legalized nature of black-white segregation. Racial segregation was rarely as rigid for Mexican Americans as it was for African Americans, even in situations where African Americans enjoyed higher economic status than Mexican Americans.


title: Mexican Americans

text: During certain periods , Mexican American children sometimes were forced to register at "Mexican schools", where classroom conditions were poor, the school year was shorter, and the quality of education was substandard.


title: Mexican Americans

text: Various reasons for the inferiority of the education given to Mexican American students have been listed by James A. Ferg-Cadima including: inadequate resources, poor equipment, unfit building construction. In 1923, the Texas Education Survey Commission found that the school year for some non-white groups was 1.6 months shorter than the average school year. Some have interpreted the shortened school year as a "means of social control" implementing policies to ensure that Mexican Americans would maintain the unskilled labor force required for a strong economy. A lesser education would serve to confine Mexican Americans to the bottom rung of the social ladder. By limiting the number of days that Mexican Americans could attend school and allotting time for these same students to work, in mainly agricultural and seasonal jobs, the prospects for higher education and upward mobility were slim.


title: Mexican Americans

text: Immigration hubs are popular destinations for Latino immigrants. These segregated areas have historically served the purpose of allowing immigrants to become comfortable in the United States, accumulate wealth, and eventually leave.


title: Mexican Americans

text: This model of immigration and residential segregation, explained above, is the model which has historically been accurate in describing the experiences of Latino immigrants. However, the patterns of immigration seen today no longer follows this model. This old model is termed the standard spatial assimilation model. More contemporary models are the polarization model and the diffusion model: The spatial assimilation model posits that as immigrants would live within this country's borders, they would simultaneously become more comfortable in their new surroundings, their socioeconomic status would rise, and their ability to speak English would increase. The combination of these changes would allow for the immigrant to move out of the barrio and into the dominant society. This type of assimilation reflects the experiences of immigrants of the early twentieth century.


title: Mexican Americans

text: Polarization model suggests that the immigration of non-black minorities into the United States further separates blacks and whites, as though the new immigrants are a buffer between them. This creates a hierarchy in which blacks are at the bottom, whites are at the top, and other groups fill the middle. In other words, the polarization model posits that Asians and Latinos are less segregated than their African-American peers because white American society would rather live closer to Asians or Latinos than African-Americans.


title: Mexican Americans

text: The diffusion model has also been suggested as a way of describing the immigrant's experience within the United States. This model is rooted in the belief that as time passes, more and more immigrants enter the country. This model suggests that as the United States becomes more populated with a more diverse set of peoples, stereotypes and discriminatory practices will decrease, as awareness and acceptance increase. The diffusion model predicts that new immigrants will break down old patterns of discrimination and prejudice, as one becomes more and more comfortable with the more diverse neighborhoods that are created through the influx of immigrants. Applying this model to the experiences of Mexican Americans forces one to see Mexican American immigrants as positive additions to the "American melting pot," in which as more additions are made to the pot, the more equal and accepting society will become.


title: Mexican Americans

text: In the heady days of the late 1960s, when the student movement was active around the globe, the Chicano movement conducted actions such as the mass walkouts by high school students in Denver and East Los Angeles in 1968 and the Chicano Moratorium in Los Angeles in 1970. The movement was particularly strong at the college level, where activists formed MEChA, an organization that seeks to promote Chicano unity and empowerment through education and political action, but also espouses revanchist ideals centered around "taking back" the American southwest for Mexican- Americans (Chicanos) through education. The new Chicano college graduate's ideal was to become empowered through education, return to his/her community and advise more chicanos to continue with their college education after high school. And upon graduation, the purpose was to return to their communities and advise other members of their families and ethnic groups to follow their footsteps. The communities political positions, and management positions were going to be reached by empowering chicanos through higher education and become involved in city councils, management positions, and politics (Pinzon, 2015)


title: Mexican Americans

text: The Chicano Moratorium, formally known as the National Chicano Moratorium Committee, was a movement of Chicano anti-war activists that built a broad-based but fragile coalition of Mexican-American groups to organize opposition to the Vietnam War. The committee was led by activists from local colleges and members of the "Brown Berets", a group with roots in the high school student movement that staged walkouts in 1968, known as the East L.A. walkouts, also called "blowouts".


title: Mexican Americans

text: The best known historical fact of the Moratorium was the death of Rubén Salazar, known for his reporting on civil rights and police brutality. The official story is that Salazar was killed by a tear gas canister fired by a member of the Los Angeles County Sheriff's Department into the Silver Dollar Café at the conclusion of the National Chicano Moratorium March.


title: Mexican Americans

text: Parents are commonly associated with being a child's first teacher. As the child grows older, the parent's role in their child's learning may change; however, a parent will often continue to serve as a role model. There are multiple research articles that have looked at parental involvement and education. A key aspect of parental involvement in education is that it can be transmitted in many ways. For a long time, there has been a misconception that the parents of Mexican American students are not involved in their children's education; however, multiple studies have demonstrated that parents are involved in their children's education (Valencia & Black, 2002). It is important to know that the parents of Mexican American students frequently display their involvement through untraditional methods; such as, consejos, home-base practices, and high academic expectations.


title: Mexican Americans

text: Literature has demonstrated that parental involvement has had a positive influence in the academic achievement of Mexican American students. Studies have shown that Mexican families show their value towards education by using untraditional methods (Kiyama, 2011). One educational practice that is commonly used among Mexican families are consejos (advice). Additional research has supported the idea that parents’ consejos have had a significant influence on the education of Mexican American students. Espino (2016) studied the influence that parental involvement had on seven, 1st generation Mexican American PhDs. The study found that one of the participant's father would frequently use consejos to encourage his son to continue his education. The father's consejos served as an encouragement tool, which motivated the participant to continue his education. Consejos are commonly associated with the parents’ occupation. Parents use their occupation as leverage to encourage their child to continue his or her education, or else they may end up working an undesirable job (Espino, 2016). While this might not be the most common form of parental involvement, studies have shown that it has been an effective tool that encourages Mexican American students. Although that might be an effective tool for Mexican American students, a mother can be just as an important figure for consejos. A mother's role teaches their child the importance of everyday tasks such as knowing how to cook, clean and care for oneself in order to be independent and also to help out around the house. The children of single mothers have a huge impact on their children in pushing them to be successful in school in order to have a better life than what they provided to their children. Most single mothers live in poverty and are dependent of the government, so they want the best for their children so they are always encouraging their children to be focused and do their best.


title: Mexican Americans

text: Another study emphasized the importance of home-based parental involvement. Altschul (2011) conducted a study that tested the effects of six different types of parental involvement and their effect on Mexican American students. The study used previous data from the National Education Longitudinal Study (NELS) of 1988. The data was used to evaluate the influence of parental practices in the 8th grade and their effect on students once they were in the 10th grade. Altschul (2011) noted that home-based parental involvement had a more positive effect on the academic achievement of Mexican American students, than involvement in school organizations. The literature suggests that parental involvement in the school setting is not necessary, parents can impact the academic achievement of their children from their home.


title: Mexican Americans

text: Additional literature has demonstrated that parent involvement also comes in the form of parent expectations. Valencia and Black (2002) argued that Mexican parents place a significant amount of value on education and hold high expectations for their children. The purpose of their study was to debunk the notion that Mexicans do not value education by providing evidence that shows the opposite. Setting high expectations and expressing their desire for their children to be academically successful has served as powerful tools to increase of the academic achievement among Mexican American students (Valencia & Black, 2002). Keith and Lichtman (1995) also conducted a research study that measured the influence of parental involvement and academic achievement. The data was collected from the NELS and used a total of 1,714 students that identified as Mexican American (Chicana/o). The study found a higher level of academic achievement among 8th grade Mexican American students and parents who had high educational aspirations for their children (Keith & Lichtman, 1995).


title: Mexican Americans

text: Additional research done by Carranza, You, Chhuon, and Hudley (2009) added support to the idea that high parental expectations were associated with higher achievement levels among Mexican American students. Carranza et al. (2009) studied 298 Mexican American high school students. They studied whether perceived parental involvement, acculturation, and self-esteem had any effect on academic achievement and aspirations. Results from their study demonstrated that perceived parental involvement had an influence on the students’ academic achievement and aspirations. Additionally, Carranza et al. noted that among females, those who perceived that their parents expected them to get good grades tended to study more and have higher academic aspirations (2009). The findings suggest that parental expectations can affect the academic performance of Mexican American students.


title: Mexican Americans

text: Based on current literature, one can conclude that parental involvement is an extremely important aspect of Mexican American students’ education. The studies demonstrated that parental involvement is not limited to participating in school activities at the school; instead, parental involvement can be displayed through various forms. There are numerous studies that suggest that parental expectations are associated with the achievement level of Mexican American students. Future research should continue to study the reasons why Mexican American students perform better when their parents expect them to do well in school. Furthermore, future research can also look into whether gender influences parental expectations.


title: Mexican Americans

text: "Stand and Deliver" was an inductee of the 2011 National Film Registry list. The National Film Board said that it was "one of the most popular of a new wave of narrative feature films produced in the 1980s by Latino filmmakers" and that it "celebrates in a direct, approachable, and impactful way, values of self-betterment through hard work and power through knowledge."


title: Mexican Americans

text: Large Mexican American populations by both size and per capita exist in the following American cities:


title: Mexican Americans

text: In the 1990s and 2000s, the Midwestern United States became a major destination for Mexican immigrants. But Mexican-Americans were already present in the Midwest's industrial cities and urban areas. Especially Mexicans/Latinos came into states like Illinois (mostly in Chicago and close-in suburbs), Indiana especially the Northern section, Iowa, Kansas, Michigan (Especially in the Western Portion of the state.), Minnesota, Missouri, Nebraska and Wisconsin due to needs of the region's industrial manufacturing base.


title: Mexican Americans

text: Another destination of Mexican and Latin American immigration was the Northeastern United States, in places such as the Monongahela Valley, Pennsylvania; Mahoning Valley, Ohio; throughout Massachusetts and the state of Rhode Island; New Haven, Connecticut along with other Latin American nationalities; Washington, D.C. with Maryland and Northern Virginia included; the Hudson Valley and Long Island of New York state; the Jersey Shore region and the Delaware Valley, New Jersey.


title: Mexican Americans

text: Communities that consist mostly of recent-arrived immigrants from Mexico, other than Texas, are also present in other parts of the rural Southern United States, in states such as Florida, Georgia, North Carolina, Tennessee, Oklahoma, Arkansas, South Carolina and Alabama. A growing Mexican-American population is also present in urban areas such as Orlando, Florida, Tampa, Florida with the Central Florida region included; the Atlanta metro area; Charlotte, North Carolina- with a majority Latino enclave of Eastland; New Orleans which increased after Hurricane Katrina in September 2005; the Hampton Roads, Virginia area; the states of Maine, New Hampshire and Delaware; and Pennsylvania especially in the Philadelphia metropolitan area.


title: Mexican Americans

text: Major cities like Boise, Idaho; Detroit, Michigan; Milwaukee, Wisconsin; Portland, Oregon; Salt Lake City, Utah; and Seattle, Washington have a large Mexican-American population.


title: Mexican Americans

text: Diabetes refers to a disease in which the body has an inefficiency of properly responding to insulin, which then affects the levels of glucose. The prevalence of diabetes in the United States is constantly rising. Common types of Diabetes are type 1 and type 2. Type 2 is the more common type of diabetes among Mexican Americans, and is constantly increasing due to poor diet habits. The increase of obesity results in an increase of type 2 diabetes among Mexican Americans in the United States. Mexican American men have higher prevalence rates in comparison to non-Latinos, whites and blacks. “The prevalence of diabetes increased from 8.9% in 1976–1980 to 12.3% in 1988–94 among adults aged 40 to 74” according to the third National Health and Nutrition Examination Survey, 1988–1994. In a 2014 study, The US Census Bureau estimates that by 2050, one in three people living in the United States will be of Latino origin including Mexican Americans. Type 2 diabetes prevalence is rising due to many risk factors and there are still many cases of pre-diabetes and undiagnosed diabetes due to lack of sources. According to the US Department of Health and Human Services (2011), individuals of Mexican descent are 50% more likely to die from diabetes than their white counterparts.


title: Yamato people

text: The (or the ) (was applied to the Imperial House of Japan or "Yamato Court" that existed in Japan in the 4th century; further, it was originally) are an ethnic group of the people that first settled in Yamato Province (modern-day Nara Prefecture). Generations of Japanese historians, linguists, and archeologists have debated whether the word is related to the earlier . The Yamato clan set up Japan's first and only dynasty. The clan became the ruling faction in the area, and incorporated native Japanese, Chinese and Korean migrants. The clan leaders also elevated their own belief system that featured ancestor worship into a national religion known as Shinto.


title: Yamato people

text: The term came to be used around the late 19th century to distinguish the settlers of mainland Japan from minority ethnic groups inhabiting the peripheral areas of the then Japanese Empire, including the Ainu, Emishi, Ryukyuans, Nivkh, Oroks, as well as Chinese, Koreans, Austronesians, and Micronesian peoples who were incorporated into the Empire of Japan in the early 20th century. After Japan's surrender in World War II, the term became antiquated for suggesting pseudoscientific racial notions that have been discarded in many circles. Japanese statistics only count their population in terms of nationality, rather than ethnicity.


title: Yamato people

text: The "Wajin" (also known as "Wa" or "Wō") or "Yamato" were the names early China used to refer to an ethnic group living in Japan around the time of the Three Kingdoms period. Chinese, Japanese, and Korean scribes regularly wrote "Wa" or "Yamato" with one and the same Chinese character 倭 until the 8th century, when the Japanese found fault with it, replacing it with 和 "harmony, peace, balance". Retroactively, this character was adopted in Japan to refer to the country itself, often combined with the character 大, literally meaning "Great", similar to Great Qing or Great Britain, so as to write the preexisting name "Yamato" (大和) (e.g., such as 大淸帝國 "Great Qing Empire" or 大英帝國 "Great British Empire"). The pronunciation "Yamato" cannot be formed from the sounds of its constituent Chinese characters; it is speculated to originally refer to a place in Japan meaning "Mountain Gate" (山戸).


title: Yamato people

text: The historical province of Yamato within Japan (now Nara Prefecture in central Honshu) borders Yamashiro Province (now the southern part of Kyoto Prefecture); however, the names of both provinces appear to contain the Japonic etymon "yama", usually meaning "mountain(s)" (but sometimes having a meaning closer to "forest", especially in some Ryukyuan languages). Some other pairs of historical provinces of Japan exhibit similar sharing of one etymological element, such as Kazusa (<*"Kami-tu-Fusa", "Upper Fusa") and Shimōsa (<*"Simo-tu-Fusa", "Lower Fusa") or Kōzuke (<*"Kami-tu-Ke", "Upper Ke") and Shimotsuke (<*"Simo-tu-Ke", "Lower Ke"). In these latter cases, the pairs of provinces with similar names are thought to have been created through the subdivision of an earlier single province in prehistoric or protohistoric times.


title: Yamato people

text: Although the etymological origins of Wa remain uncertain, Chinese historical texts recorded an ancient people residing in the Japanese archipelago, named something like *"ʼWâ" or *"ʼWər" 倭. Carr surveys prevalent proposals for the etymology of "Wa" ranging from feasible (transcribing Japanese first-person pronouns "waga" 我が "my; our" and "ware" 我 "I; we; oneself") to shameful (writing Japanese "Wa" as 倭 implying "dwarf"), and summarizes interpretations for *"ʼWâ" "Japanese" into variations on two etymologies: "behaviorally 'submissive' or physically 'short. The first "submissive; obedient" explanation began with the (121 CE) "Shuowen Jiezi" dictionary. It defines 倭 as "shùnmào" 順皃 "obedient/submissive/docile appearance", graphically explains the "person; human' radical with a "wěi" 委 "bent" phonetic, and quotes the above "Shi Jing" poem. "Conceivably, when Chinese first met Japanese," Carr suggests, "they transcribed "Wa" as *"ʼWâ" 'bent back' signifying 'compliant' bowing/obeisance. Bowing is noted in early historical references to Japan." Examples include "Respect is shown by squatting", and "they either squat or kneel, with both hands on the ground. This is the way they show respect."


title: Yamato people

text: Koji Nakayama interprets "wēi" 逶 "winding" as "very far away" and euphemistically translates "Wō" 倭 as "separated from the continent". The second etymology of "wō" 倭 meaning "dwarf (variety of an animal or plant species), midget, little people" has possible cognates in "ǎi" 矮 "low, short (of stature)", "wō" 踒 "strain; sprain; bent legs", and "wò" 臥 "lie down; crouch; sit (animals and birds)". Early Chinese dynastic histories refer to a "Zhūrúguó" 侏儒國 "pygmy/dwarf country" located south of Japan, associated with possibly Okinawa Island or the Ryukyu Islands. Carr cites the historical precedence of construing Wa as "submissive people" and the "Country of Dwarfs" legend as evidence that the "little people" etymology was a secondary development.


title: Yamato people

text: In the 6th century, the Yamato dynasty—one of many tribes, of various origins, who had settled Japan in prehistory—founded a state modeled on the Chinese states of Sui and Tang, the center of East Asian political influence at the time. As the Yamato influence expanded, their Old Japanese language became the common spoken language.


title: Yamato people

text: Scientific racism was a Western idea that was imported from the late nineteenth century onward. Despite being hotly contested by Japanese scholars, the false notion of racial homogeneity was used as propaganda because of the political circumstances of late nineteenth- and early twentieth-century Japan, which coincided with Japanese imperialism and World War II. Pseudoscientific racial theories, which included the false belief of the superiority of the Yamato character, were used to justify military expansionism, discriminatory practices, and ethnocentrism. The concept of "pure blood" as a criterion for the uniqueness of the Yamato "minzoku" began circulating around 1880 in Japan, around the time some Japanese scientists began investigations into eugenics.


title: Yamato people

text: Initially, in order to justify Japan's conquest of Asia, Japanese propaganda espoused the ideas of Japanese supremacy by claiming that the Japanese represented a combination of all Asian peoples and cultures, emphasizing heterogeneous traits. Japanese propaganda started to place an emphasis on the ideas of racial purity and the supremacy of the Yamato race when the Second Sino-Japanese War intensified. Driven by the ideology of racial supremacy, racial purity and national unity, between 1868 and the 1940s, the Japanese government carefully identified and forcefully assimilated marginalized populations, which included Okinawans, the Ainu, and other underrepresented groups, imposing assimilation programs in language, culture and religion.


title: Yamato people

text: According to Aya Fujiwara, a postdoctoral Fellow at McMaster University, in an attempt to have some influence over the Japanese diaspora in Canada, Japanese authorities used the term Yamato as race propaganda during World War 2, saying that: "For Japanese-Canadians in particular, the Emperor was the most natural symbol to promote primordial national sentiment and superiority of the Yamato race — the term that the Japanese used to distinguish themselves from others. This term meant a noble race, the members of which saw themselves as “chosen people.” The modernization of Japan, which began with the Meiji Restoration in 1868, produced a number of historical writings that tried to define the Japanese under the official scheme to create a strong nation. Imported to Canada by Japanese intellectuals, a “common myth of descent” that Japanese people belonged to the noble Yamato race headed by the Emperor since the ancient period was one of the core elements that defined Japanese-Canadian ethno-racial identity in the 1920s and the 1930s. The evolution and survival of an ethnic community, Anthony D. Smith argues, relies on the complicated “belief-system” that creates “a sacred communion of the people” with cultural and historical distinctiveness. During this period, Japanese intellectuals, scholars, and official representatives sought to keep Japanese Canadians within their sphere of influence, thereby reinforcing a transnational myth that would promote Japanese Canadians’ sense of racial pride as God’s chosen people in the world."


title: Yamato people

text: At the end of the World War II, the Japanese government continued to adhere to the notions of racial homogeneity and racial supremacy, with the Yamato race at the top of the racial hierarchy. Japanese propaganda of racial purity returned to post-World War II Japan because of the support of the Allied forces. U.S. policy in Japan terminated the purge of high-ranking fascist war criminals and reinstalled the leaders who were responsible for the creation and manifestation of prewar race propaganda.


title: Yamato people

text: In present-day Japan, the term Yamato "minzoku" may be seen as antiquated for connoting racial notions that have been discarded in many circles since Japan's surrender in World War II. "Japanese people" or even "Japanese-Japanese" are often used instead, although these terms also have complications owing to their ambiguous blending of notions of ethnicity and nationality.


title: Yamato people

text: In present-day Japan statistics only counts their population in terms of nationality, rather than ethnicity, thus the number of ethnic Yamato and their actual population numbers are ambiguous.


title: Yamato people

text: The most well-regarded theory is that present-day Yamato Japanese are descedants from both the Yayoi people and the various local Jōmon people. Japanese people belong to the East Asian lineages D-M55 and O-M175, with a minority belonging to C-M217 and N-M231. The reference population for the Japanese (Yamato) used in Geno 2.0 Next Generation is 89% East Asia, 2% Finland and Northern Siberia, 2% Central Asia, and 7% Southeast Asia & Oceania, making Japanese approximately ~100% East-Eurasian. Genealogical research has indicated extremely similar genetic profiles between these groups, making them nearly indistinguishable from each other and ancient samples. Japanese people were found to share high genetic affinity with the ancient (~8,000 BC) "Devils_Gate_N" sample in the Amur region of Northeast Asia.


title: Yamato people

text: The earliest written records about people in Japan are from Chinese sources. These sources spoke about the Wa people, the direct ancestors of the Yamato and other Japonic agriculturalists. The Wa of Na received a golden seal from the Emperor Guangwu of the Later Han dynasty. This event was recorded in the "Book of the Later Han" compiled by Fan Ye in the 5th century. The seal itself was discovered in northern Kyūshū in the 18th century. Early Chinese historians described Wa as a land of hundreds of scattered tribal communities. Third-century Chinese sources reported that the Wa/early Yamato lived on raw fish, vegetables, and rice served on bamboo and wooden trays, clapped their hands in worship (something still done in Shinto shrines today), and built earthen-grave mounds. They also maintained vassal-master relations, collected taxes, had provincial granaries and markets, and observed mourning. The "Wei Zhi" (), which is part of the Records of the three Kingdoms, first mentions Yamataikoku and Queen Himiko in the 3rd century. According to the record, Himiko assumed the throne of Wa, as a spiritual leader, after a major civil war. Her younger brother was in charge of the affairs of state, including diplomatic relations with the Chinese court of the Kingdom of Wei. When asked about their origins by the Wei embassy, the people of Wa claimed to be descendants of the people of Wu, a historic figure of the Wu Kingdom around the Yangtze Delta of China, however this is disputed.


title: Yamato people

text: Japonic speakers were also present on the southern and central "Korean Peninsula". These "Peninsular Japonic agriculturalists" were later replaced/assimilated by Koreanic-speakers (from southern Manchuria) likely causing the Yayoi migration and expansion within the Japanese archipelago. Whitman (2012) suggests that the Yayoi agriculturalists are not related to the proto-Koreans but that they were present on the Korean peninsula during the Mumun pottery period. According to him, Japonic arrived in the Korean peninsula around 1500 BC and was brought to the Japanese archipelago by the Yayoi agriculturalists at around 950 BC, during the late Jōmon period. The language family associated with both Mumun and Yayoi culture is Japonic. Koreanic arrived later from Manchuria to the Korean peninsula at around 300 BC and coexist with the descendants of the Japonic Mumun cultivators (or assimilated them). Both had influence on each other and a later founder effect diminished the internal variety of both language families.


title: Yamato people

text: A genetic study (2019) estimated that modern Japanese (Yamato) share more than 90% of their genome with the Yayoi rice agriculturalists and less than 10% with the heterogeneous Jōmon period groups. A more recent study by Gakuhari et al. 2019 estimates that modern Japanese people have between 92% to 96,7% Yayoi rice-agriculturalist ancestry (with the 3.3% to 8% from the heterogeneous Jōmon period tribes) and cluster closely with other Koreans and Han-Chinese, but are slightly with shifted towards eastern Siberians.


title: Yamato people

text: Based on archaeological evidence and the genetic similarity between modern Japanese and Koreans, Jared Diamond said that the Yayoi people, the ancestors of the Yamato people, migrated from the Korean peninsula.


title: Yamato people

text: Watanabe et al. 2021 found that the Jōmon people were a heterogeneous population and that Japanese from different regions had different amounts of Jōmon-derived SNP alleles, ranging from 17.3% to 24% samplified by southern Jōmon, and 3.8% to 14.9% samplified by northern Jōmon. Southern Jōmon were genetically similar to contemporary East Asians (especially Tujia people, Tibetan people and Miao people), while northern Jōmon had a partial distinct ancestry component, possibly deriving from Paleolithic Siberians, next to an East Asian ancestry component. The Jōmon period population, although heterogeneous, were closest to contemporary East Asians and Native Americans.


title: Yamato people

text: In 2021, new research from a study published in the journal Science Advances found that the people of Japan bore genetic signatures from three ancient populations rather than just two as previously thought.


title: Yamato people

text: The first was Japan's indigenous culture of hunter-gatherers called the Jomon, dating to roughly 15,000 years ago. The second was a population of Northeast Asian origins called the Yayoi, who arrived at about 900 BC, bringing wet-rice farming to Japan. According to the researchers, Japanese people has approximately 13% and 16% genetic ancestry from these two groups respectively.


title: Yamato people

text: The remaining 71% of genetic ancestry was found to come from migrants that arrived around 300 AD during the Kofun period, and had genetic makeup mainly resembling the Han Chinese population of China. This migrant group was said to have brought cultural advances and centralised leadership to Japan. According to Shigeki Nakagome, co-leader of the study, "Chinese characters started to be used in this period, such as Chinese characters inscribed on metal implements, for example swords."


title: Yamato people

text: A new study in 2022 conducted by the University of Xiamen shed light on the lack of Jōmon genomes found in present-day Koreans and Japanese. Researchers discovered that despite finding evidence of the Jōmon people on the Korean peninsula and the Japanese archipelago, there were little to no traces left of their genetic impact in their respective people's gene pools. According to the study, Ancient Koreans were composed of "northern East Asian-related ancestry and indigenous Jōmon-related ancestry" where the "northern East Asian ancestry was suggested to be related to the Neolithic West Liao River farmers in northeast China". The finding indicated that the "West Liao River-related farmers might have spread the proto-Korean language as their ancestry was found to be predominant in extant Koreans" and these "Proto-Korean groups, in turn, introduced West Liao River-like ancestry into the gene pool of present-day Japan". These people are thought to have caused the displacement of the indigenous Jōmon people causing a significant diminishment of Jōmon genomes in the regions. It was deduced that this event (and the populations remaining genetically homogeneous since then) was what caused modern Koreans and Japanese to share the majority of their genetic makeup as the latter group "can be represented as a mixture of Koreans (91%) with a limited genetic heritage from a basal East Asian lineage related to Jōmon (9%)".


title: Yamato people

text: Major disagreements exists as to whether the Ryukyuans are considered the same as the Yamato, or identified as an independent but related ethnic group, or as a sub-group that constitutes Japanese ethnicity together with the Yamato. Ryukyuans have a distinct culture from the Yamato, with its own native cuisine, history, language, religion and traditions.


title: Yamato people

text: From the Meiji period onward, by which the Ryukyuan's kingdom was annexed by Japan, Japanese scholars such as Shinobu Orikuchi and Kunio Yanagita supported the later discredited ideological viewpoint that they were a sub-group of the Yamato people. The Ryukyuans were forcibly assimilated into Japanese (Yamato) people with their ethnic identity suppressed by the Meiji government, and suppressed Ryukyuan ethnic identity, tradition, culture and language. Many modern day Japanese people today that colonized the Ryukyu Islands are a mixture of both Yamato and Ryukyuan.


title: Chloroplast

text: A chloroplast () is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water in the cells. The ATP and NADPH is then used to make organic molecules from carbon dioxide in a process known as the Calvin cycle. Chloroplasts carry out a number of other functions, including fatty acid synthesis, amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from one, in unicellular algae, up to 100 in plants like "Arabidopsis" and wheat.


title: Chloroplast

text: A chloroplast is characterized by its two membranes and a high concentration of chlorophyll. Other plastid types, such as the leucoplast and the chromoplast, contain little chlorophyll and do not carry out photosynthesis.


title: Chloroplast

text: Chloroplasts are highly dynamic—they circulate and are moved around within plant cells, and occasionally pinch in two to reproduce. Their behavior is strongly influenced by environmental factors like light color and intensity. Chloroplasts, like mitochondria, contain their own DNA, which is thought to be inherited from their ancestor—a photosynthetic cyanobacterium that was engulfed by an early eukaryotic cell. Chloroplasts cannot be made by the plant cell and must be inherited by each daughter cell during cell division.


title: Chloroplast

text: With one exception (the amoeboid "Paulinella chromatophora"), all chloroplasts can probably be traced back to a single endosymbiotic event, when a cyanobacterium was engulfed by the eukaryote. Despite this, chloroplasts can be found in an extremely wide set of organisms, some not even directly related to each other—a consequence of many secondary and even tertiary endosymbiotic events.


title: Chloroplast

text: The word "chloroplast" is derived from the Greek words "chloros" (χλωρός), which means green, and "plastes" (πλάστης), which means "the one who forms".


title: Chloroplast

text: The first definitive description of a chloroplast ("Chlorophyllkörnen", "grain of chlorophyll") was given by Hugo von Mohl in 1837 as discrete bodies within the green plant cell. In 1883, Andreas Franz Wilhelm Schimper would name these bodies as "chloroplastids" ("Chloroplastiden"). In 1884, Eduard Strasburger adopted the term "chloroplasts" ("Chloroplasten").


title: Chloroplast

text: Chloroplasts are one of many types of organelles in the plant cell. They are considered to have evolved from endosymbiotic cyanobacteria. Mitochondria are thought to have come from a similar endosymbiosis event, where an aerobic prokaryote was engulfed. This origin of chloroplasts was first suggested by the Russian biologist Konstantin Mereschkowski in 1905 after Andreas Franz Wilhelm Schimper observed in 1883 that chloroplasts closely resemble cyanobacteria. Chloroplasts are only found in plants, algae, and three species of amoeba – "Paulinella chromatophora", "P. micropora", and marine "P. longichromatophora".


title: Chloroplast

text: Chloroplasts are considered endosymbiotic Cyanobacteria. Cyanobacteria are sometimes called blue-green algae even though they are prokaryotes. They are a diverse phylum of gram-negative bacteria capable of carrying out photosynthesis. Cyanobacteria also contain a peptidoglycan cell wall, which is thicker than in other gram-negative bacteria, and which is located between their two cell membranes. Like chloroplasts, they have thylakoids within them. On the thylakoid membranes are photosynthetic pigments, including chlorophyll "a". Phycobilins are also common cyanobacterial pigments, usually organized into hemispherical phycobilisomes attached to the outside of the thylakoid membranes (phycobilins are not shared with all chloroplasts though).


title: Chloroplast

text: a free-living cyanobacterium entered an early eukaryotic cell, either as food or as an internal parasite, but managed to escape the phagocytic vacuole it was contained in. The two innermost lipid-bilayer membranes that surround all chloroplasts correspond to the outer and inner membranes of the ancestral cyanobacterium's gram negative cell wall, and not the phagosomal membrane from the host, which was probably lost.


title: Chloroplast

text: The new cellular resident quickly became an advantage, providing food for the eukaryotic host, which allowed it to live within it. Over time, the cyanobacterium was assimilated, and many of its genes were lost or transferred to the nucleus of the host. From genomes that probably originally contained over 3000 genes only about 130 genes remain in the chloroplasts of contemporary plants. Some of its proteins were then synthesized in the cytoplasm of the host cell, and imported back into the chloroplast (formerly the cyanobacterium). Separately, somewhere about 90–140 million years ago, it happened again and led to the amoeboid "Paulinella chromatophora".


title: Chloroplast

text: This event is called "endosymbiosis", or "cell living inside another cell with a mutual benefit for both". The external cell is commonly referred to as the "host" while the internal cell is called the "endosymbiont".


title: Chloroplast

text: Chloroplasts are believed to have arisen after mitochondria, since all eukaryotes contain mitochondria, but not all have chloroplasts. This is called "serial endosymbiosis"—an early eukaryote engulfing the mitochondrion ancestor, and some descendants of it then engulfing the chloroplast ancestor, creating a cell with both chloroplasts and mitochondria.


title: Chloroplast

text: Whether or not primary chloroplasts came from a single endosymbiotic event, or many independent engulfments across various eukaryotic lineages, has long been debated. It is now generally held that organisms with primary chloroplasts share a single ancestor that took in a cyanobacterium 600–2000 million years ago. It has been proposed this the closest living relative of this bacterium is "Gloeomargarita lithophora." The exception is the amoeboid "Paulinella chromatophora", which descends from an ancestor that took in a "Prochlorococcus" cyanobacterium 90–500 million years ago.


title: Chloroplast

text: These chloroplasts, which can be traced back directly to a cyanobacterial ancestor, are known as "primary plastids" (""plastid"" in this context means almost the same thing as chloroplast). All primary chloroplasts belong to one of four chloroplast lineages—the glaucophyte chloroplast lineage, the amoeboid "Paulinella chromatophora" lineage, the rhodophyte (red algal) chloroplast lineage, or the chloroplastidan (green) chloroplast lineage. The rhodophyte and chloroplastidan lineages are the largest, with chloroplastidan (green) being the one that contains the land plants.


title: Chloroplast

text: Usually the endosymbiosis event is considered to have occurred in the Archaeplastida, within which the glaucophyta being the possible earliest diverging lineage. The glaucophyte chloroplast group is the smallest of the three primary chloroplast lineages, being found in only 13 species, and is thought to be the one that branched off the earliest. Glaucophytes have chloroplasts that retain a peptidoglycan wall between their double membranes, like their cyanobacterial parent. For this reason, glaucophyte chloroplasts are also known as 'muroplasts' (besides 'cyanoplasts' or 'cyanelles'). Glaucophyte chloroplasts also contain concentric unstacked thylakoids, which surround a carboxysome – an icosahedral structure that glaucophyte chloroplasts and cyanobacteria keep their carbon fixation enzyme RuBisCO in. The starch that they synthesize collects outside the chloroplast. Like cyanobacteria, glaucophyte and rhodophyte chloroplast thylakoids are studded with light collecting structures called phycobilisomes. For these reasons, glaucophyte chloroplasts are considered a primitive intermediate between cyanobacteria and the more evolved chloroplasts in red algae and plants.


title: Chloroplast

text: The rhodophyte, or red algae chloroplast group is another large and diverse chloroplast lineage. Rhodophyte chloroplasts are also called "rhodoplasts", literally "red chloroplasts".


title: Chloroplast

text: Rhodoplasts have a double membrane with an intermembrane space and phycobilin pigments organized into phycobilisomes on the thylakoid membranes, preventing their thylakoids from stacking. Some contain pyrenoids. Rhodoplasts have chlorophyll "a" and phycobilins for photosynthetic pigments; the phycobilin phycoerythrin is responsible for giving many red algae their distinctive red color. However, since they also contain the blue-green chlorophyll "a" and other pigments, many are reddish to purple from the combination. The red phycoerytherin pigment is an adaptation to help red algae catch more sunlight in deep water—as such, some red algae that live in shallow water have less phycoerythrin in their rhodoplasts, and can appear more greenish. Rhodoplasts synthesize a form of starch called floridean starch, which collects into granules outside the rhodoplast, in the cytoplasm of the red alga.


title: Chloroplast

text: The chloroplastida chloroplasts, or green chloroplasts, are another large, highly diverse primary chloroplast lineage. Their host organisms are commonly known as green algae and land plants. They differ from glaucophyte and red algal chloroplasts in that they have lost their phycobilisomes, and contain chlorophyll "b" instead. Most green chloroplasts are (obviously) green, though some aren't, like some forms of "Hæmatococcus pluvialis", due to accessory pigments that override the chlorophylls' green colors. Chloroplastida chloroplasts have lost the peptidoglycan wall between their double membrane, leaving an intermembrane space. Some plants seem to have kept the genes for the synthesis of the peptidoglycan layer, though they've been repurposed for use in chloroplast division instead.


title: Chloroplast

text: Green algae and plants keep their starch "inside" their chloroplasts, and in plants and some algae, the chloroplast thylakoids are arranged in grana stacks. Some green algal chloroplasts contain a structure called a pyrenoid, which is functionally similar to the glaucophyte carboxysome in that it is where RuBisCO and CO are concentrated in the chloroplast.


title: Chloroplast

text: "Helicosporidium" is a genus of nonphotosynthetic parasitic green algae that is thought to contain a vestigial chloroplast. Genes from a chloroplast and nuclear genes indicating the presence of a chloroplast have been found in "Helicosporidium" even if nobody's seen the chloroplast itself.


title: Chloroplast

text: While most chloroplasts originate from that first set of endosymbiotic events, "Paulinella chromatophora" is an exception that acquired a photosynthetic cyanobacterial endosymbiont more recently. It is not clear whether that symbiont is closely related to the ancestral chloroplast of other eukaryotes. Being in the early stages of endosymbiosis, "Paulinella chromatophora" can offer some insights into how chloroplasts evolved. "Paulinella" cells contain one or two sausage-shaped blue-green photosynthesizing structures called chromatophores, descended from the cyanobacterium "Synechococcus". Chromatophores cannot survive outside their host. Chromatophore DNA is about a million base pairs long, containing around 850 protein-encoding genes—far less than the three million base pair "Synechococcus" genome, but much larger than the approximately 150,000 base pair genome of the more assimilated chloroplast. Chromatophores have transferred much less of their DNA to the nucleus of their host. About 0.3–0.8% of the nuclear DNA in "Paulinella" is from the chromatophore, compared with 11–14% from the chloroplast in plants.


title: Chloroplast

text: Many other organisms obtained chloroplasts from the primary chloroplast lineages through secondary endosymbiosis—engulfing a red or green alga that contained a chloroplast. These chloroplasts are known as secondary plastids.


title: Chloroplast

text: While primary chloroplasts have a double membrane from their cyanobacterial ancestor, secondary chloroplasts have additional membranes outside of the original two, as a result of the secondary endosymbiotic event, when a nonphotosynthetic eukaryote engulfed a chloroplast-containing alga but failed to digest it—much like the cyanobacterium at the beginning of this story. The engulfed alga was broken down, leaving only its chloroplast, and sometimes its cell membrane and nucleus, forming a chloroplast with three or four membranes—the two cyanobacterial membranes, sometimes the eaten alga's cell membrane, and the phagosomal vacuole from the host's cell membrane.


title: Chloroplast

text: The genes in the phagocytosed eukaryote's nucleus are often transferred to the secondary host's nucleus.


title: Chloroplast

text: Cryptomonads and chlorarachniophytes retain the phagocytosed eukaryote's nucleus, an object called a nucleomorph, located between the second and third membranes of the chloroplast.


title: Chloroplast

text: All secondary chloroplasts come from green and red algae—no secondary chloroplasts from glaucophytes have been observed, probably because glaucophytes are relatively rare in nature, making them less likely to have been taken up by another eukaryote.


title: Chloroplast

text: Green algae have been taken up by the euglenids, chlorarachniophytes, a lineage of dinoflagellates, and possibly the ancestor of the CASH lineage (cryptomonads, alveolates, stramenopiles and haptophytes) in three or four separate engulfments. Many green algal derived chloroplasts contain pyrenoids, but unlike chloroplasts in their green algal ancestors, storage product collects in granules outside the chloroplast.


title: Chloroplast

text: Euglenophytes are a group of common flagellated protists that contain chloroplasts derived from a green alga. Euglenophyte chloroplasts have three membranes—it is thought that the membrane of the primary endosymbiont was lost, leaving the cyanobacterial membranes, and the secondary host's phagosomal membrane. Euglenophyte chloroplasts have a pyrenoid and thylakoids stacked in groups of three. Photosynthetic product is stored in the form of paramylon, which is contained in membrane-bound granules in the cytoplasm of the euglenophyte.


title: Chloroplast

text: Chlorarachniophytes are a rare group of organisms that also contain chloroplasts derived from green algae, though their story is more complicated than that of the euglenophytes. The ancestor of chlorarachniophytes is thought to have been a eukaryote with a "red" algal derived chloroplast. It is then thought to have lost its first red algal chloroplast, and later engulfed a green alga, giving it its second, green algal derived chloroplast.


title: Chloroplast

text: Chlorarachniophyte chloroplasts are bounded by four membranes, except near the cell membrane, where the chloroplast membranes fuse into a double membrane. Their thylakoids are arranged in loose stacks of three. Chlorarachniophytes have a form of polysaccharide called chrysolaminarin, which they store in the cytoplasm, often collected around the chloroplast pyrenoid, which bulges into the cytoplasm.


title: Chloroplast

text: Chlorarachniophyte chloroplasts are notable because the green alga they are derived from has not been completely broken down—its nucleus still persists as a nucleomorph found between the second and third chloroplast membranes—the periplastid space, which corresponds to the green alga's cytoplasm.


title: Chloroplast

text: "Lepidodinium viride" and its close relatives are dinophytes (see below) that lost their original peridinin chloroplast and replaced it with a green algal derived chloroplast (more specifically, a prasinophyte). "Lepidodinium" is the only dinophyte that has a chloroplast that's not from the rhodoplast lineage. The chloroplast is surrounded by two membranes and has no nucleomorph—all the nucleomorph genes have been transferred to the dinophyte nucleus. The endosymbiotic event that led to this chloroplast was serial secondary endosymbiosis rather than tertiary endosymbiosis—the endosymbiont was a green alga containing a primary chloroplast (making a secondary chloroplast).


title: Chloroplast

text: Cryptophytes, or cryptomonads are a group of algae that contain a red-algal derived chloroplast. Cryptophyte chloroplasts contain a nucleomorph that superficially resembles that of the chlorarachniophytes. Cryptophyte chloroplasts have four membranes, the outermost of which is continuous with the rough endoplasmic reticulum. They synthesize ordinary starch, which is stored in granules found in the periplastid space—outside the original double membrane, in the place that corresponds to the red alga's cytoplasm. Inside cryptophyte chloroplasts is a pyrenoid and thylakoids in stacks of two.


title: Chloroplast

text: Their chloroplasts do not have phycobilisomes, but they do have phycobilin pigments which they keep in their thylakoid space, rather than anchored on the outside of their thylakoid membranes.


title: Chloroplast

text: Haptophytes are similar and closely related to cryptophytes or heterokontophytes. Their chloroplasts lack a nucleomorph, their thylakoids are in stacks of three, and they synthesize chrysolaminarin sugar, which they store completely outside of the chloroplast, in the cytoplasm of the haptophyte.


title: Chloroplast

text: The heterokontophytes, also known as the stramenopiles, are a very large and diverse group of eukaryotes. The photoautotrophic lineage, Ochrophyta, including the diatoms and the brown algae, golden algae, and yellow-green algae, also contains red algal derived chloroplasts.


title: Chloroplast

text: Heterokont chloroplasts are very similar to haptophyte chloroplasts, containing a pyrenoid, triplet thylakoids, and with some exceptions, having four layer plastidic envelope, the outermost epiplastid membrane connected to the endoplasmic reticulum. Like haptophytes, heterokontophytes store sugar in chrysolaminarin granules in the cytoplasm. Heterokontophyte chloroplasts contain chlorophyll "a" and with a few exceptions chlorophyll "c", but also have carotenoids which give them their many colors.


title: Chloroplast

text: The alveolates are a major clade of unicellular eukaryotes of both autotrophic and heterotrophic members. The most notable shared characteristic is the presence of cortical (outer-region) alveoli (sacs). These are flattened vesicles (sacs) packed into a continuous layer just under the membrane and supporting it, typically forming a flexible pellicle (thin skin). In dinoflagellates they often form armor plates. Many members contain a red-algal derived plastid. One notable characteristic of this diverse group is the frequent loss of photosynthesis. However, a majority of these heterotrophs continue to process a non-photosynthetic plastid.


title: Chloroplast

text: Apicomplexans are a group of alveolates. Like the helicosproidia, they're parasitic, and have a nonphotosynthetic chloroplast. They were once thought to be related to the helicosproidia, but it is now known that the helicosproida are green algae rather than part of the CASH lineage. The apicomplexans include "Plasmodium", the malaria parasite. Many apicomplexans keep a vestigial red algal derived chloroplast called an apicoplast, which they inherited from their ancestors. Other apicomplexans like "Cryptosporidium" have lost the chloroplast completely. Apicomplexans store their energy in amylopectin granules that are located in their cytoplasm, even though they are nonphotosynthetic.


title: Chloroplast

text: Apicoplasts have lost all photosynthetic function, and contain no photosynthetic pigments or true thylakoids. They are bounded by four membranes, but the membranes are not connected to the endoplasmic reticulum. The fact that apicomplexans still keep their nonphotosynthetic chloroplast around demonstrates how the chloroplast carries out important functions other than photosynthesis. Plant chloroplasts provide plant cells with many important things besides sugar, and apicoplasts are no different—they synthesize fatty acids, isopentenyl pyrophosphate, iron-sulfur clusters, and carry out part of the heme pathway. This makes the apicoplast an attractive target for drugs to cure apicomplexan-related diseases. The most important apicoplast function is isopentenyl pyrophosphate synthesis—in fact, apicomplexans die when something interferes with this apicoplast function, and when apicomplexans are grown in an isopentenyl pyrophosphate-rich medium, they dump the organelle.


title: Chloroplast

text: The Chromerida is a newly discovered group of algae from Australian corals which comprises some close photosynthetic relatives of the apicomplexans. The first member, "Chromera velia", was discovered and first isolated in 2001. The discovery of "Chromera velia" with similar structure to the apicomplexanss, provides an important link in the evolutionary history of the apicomplexans and dinophytes. Their plastids have four membranes, lack chlorophyll c and use the type II form of RuBisCO obtained from a horizontal transfer event.


title: Chloroplast

text: The dinoflagellates are yet another very large and diverse group of protists, around half of which are (at least partially) photosynthetic.


title: Chloroplast

text: Most dinophyte chloroplasts are secondary red algal derived chloroplasts. Many other dinophytes have lost the chloroplast (becoming the nonphotosynthetic kind of dinoflagellate), or replaced it though "tertiary" endosymbiosis—the engulfment of another eukaryotic algae containing a red algal derived chloroplast. Others replaced their original chloroplast with a green algal derived one.


title: Chloroplast

text: Most dinophyte chloroplasts contain form II RuBisCO, at least the photosynthetic pigments chlorophyll "a", chlorophyll "c", "beta"-carotene, and at least one dinophyte-unique xanthophyll (peridinin, dinoxanthin, or diadinoxanthin), giving many a golden-brown color. All dinophytes store starch in their cytoplasm, and most have chloroplasts with thylakoids arranged in stacks of three.


title: Chloroplast

text: The most common dinophyte chloroplast is the peridinin-type chloroplast, characterized by the carotenoid pigment peridinin in their chloroplasts, along with chlorophyll "a" and chlorophyll "c". Peridinin is not found in any other group of chloroplasts. The peridinin chloroplast is bounded by three membranes (occasionally two), having lost the red algal endosymbiont's original cell membrane. The outermost membrane is not connected to the endoplasmic reticulum. They contain a pyrenoid, and have triplet-stacked thylakoids. Starch is found outside the chloroplast. An important feature of these chloroplasts is that their chloroplast DNA is highly reduced and fragmented into many small circles. Most of the genome has migrated to the nucleus, and only critical photosynthesis-related genes remain in the chloroplast.


title: Chloroplast

text: The peridinin chloroplast is thought to be the dinophytes' "original" chloroplast, which has been lost, reduced, replaced, or has company in several other dinophyte lineages.


title: Chloroplast

text: The fucoxanthin dinophyte lineages (including "Karlodinium" and "Karenia") lost their original red algal derived chloroplast, and replaced it with a new chloroplast derived from a haptophyte endosymbiont. "Karlodinium" and "Karenia" probably took up different heterokontophytes. Because the haptophyte chloroplast has four membranes, tertiary endosymbiosis would be expected to create a six membraned chloroplast, adding the haptophyte's cell membrane and the dinophyte's phagosomal vacuole. However, the haptophyte was heavily reduced, stripped of a few membranes and its nucleus, leaving only its chloroplast (with its original double membrane), and possibly one or two additional membranes around it.


title: Chloroplast

text: Fucoxanthin-containing chloroplasts are characterized by having the pigment fucoxanthin (actually 19′-hexanoyloxy-fucoxanthin and/or 19′-butanoyloxy-fucoxanthin) and no peridinin. Fucoxanthin is also found in haptophyte chloroplasts, providing evidence of ancestry.


title: Chloroplast

text: Some dinophytes, like "Kryptoperidinium" and "Durinskia", have a diatom (heterokontophyte)-derived chloroplast. These chloroplasts are bounded by up to "five" membranes, (depending on whether the entire diatom endosymbiont is counted as the chloroplast, or just the red algal derived chloroplast inside it). The diatom endosymbiont has been reduced relatively little—it still retains its original mitochondria, and has endoplasmic reticulum, ribosomes, a nucleus, and of course, red algal derived chloroplasts—practically a complete cell, all inside the host's endoplasmic reticulum lumen. However the diatom endosymbiont can't store its own food—its storage polysaccharide is found in granules in the dinophyte host's cytoplasm instead. The diatom endosymbiont's nucleus is present, but it probably can't be called a nucleomorph because it shows no sign of genome reduction, and might have even been "expanded". Diatoms have been engulfed by dinoflagellates at least three times.


title: Chloroplast

text: The diatom endosymbiont is bounded by a single membrane, inside it are chloroplasts with four membranes. Like the diatom endosymbiont's diatom ancestor, the chloroplasts have triplet thylakoids and pyrenoids.


title: Chloroplast

text: In some of these genera, the diatom endosymbiont's chloroplasts aren't the only chloroplasts in the dinophyte. The original three-membraned peridinin chloroplast is still around, converted to an eyespot.


title: Chloroplast

text: In some groups of mixotrophic protists, like some dinoflagellates (e.g. "Dinophysis"), chloroplasts are separated from a captured alga and used temporarily. These klepto chloroplasts may only have a lifetime of a few days and are then replaced.


title: Chloroplast

text: Members of the genus "Dinophysis" have a phycobilin-containing chloroplast taken from a cryptophyte. However, the cryptophyte is not an endosymbiont—only the chloroplast seems to have been taken, and the chloroplast has been stripped of its nucleomorph and outermost two membranes, leaving just a two-membraned chloroplast. Cryptophyte chloroplasts require their nucleomorph to maintain themselves, and "Dinophysis" species grown in cell culture alone cannot survive, so it is possible (but not confirmed) that the "Dinophysis" chloroplast is a kleptoplast—if so, "Dinophysis" chloroplasts wear out and "Dinophysis" species must continually engulf cryptophytes to obtain new chloroplasts to replace the old ones.


title: Chloroplast

text: Chloroplasts, like other types of plastid, contain a genome separate from that in the cell nucleus. The existence of chloroplast DNA (cpDNA) was identified biochemically in 1959, and confirmed by electron microscopy in 1962. The discoveries that the chloroplast contains ribosomes and performs protein synthesis revealed that the chloroplast is genetically semi-autonomous. Chloroplast DNA was first sequenced in 1986. Since then, hundreds of chloroplast DNAs from various species have been sequenced, but they are mostly those of land plants and green algae—glaucophytes, red algae, and other algal groups are extremely underrepresented, potentially introducing some bias in views of "typical" chloroplast DNA structure and content.


title: Chloroplast

text: With few exceptions, most chloroplasts have their entire chloroplast genome combined into a single large circular DNA molecule, typically 120,000–170,000 base pairs long. They can have a contour length of around 30–60 micrometers, and have a mass of about 80–130 million daltons.


title: Chloroplast

text: While usually thought of as a circular molecule, there is some evidence that chloroplast DNA molecules more often take on a linear shape.


title: Chloroplast

text: Many chloroplast DNAs contain two "inverted repeats", which separate a long single copy section (LSC) from a short single copy section (SSC).


title: Chloroplast

text: While a given pair of inverted repeats are rarely completely identical, they are always very similar to each other, apparently resulting from concerted evolution.


title: Chloroplast

text: The inverted repeats vary wildly in length, ranging from 4,000 to 25,000 base pairs long each and containing as few as four or as many as over 150 genes. Inverted repeats in plants tend to be at the upper end of this range, each being 20,000–25,000 base pairs long.


title: Chloroplast

text: The inverted repeat regions are highly conserved among land plants, and accumulate few mutations. Similar inverted repeats exist in the genomes of cyanobacteria and the other two chloroplast lineages (glaucophyta and rhodophyceae), suggesting that they predate the chloroplast, though some chloroplast DNAs have since lost or flipped the inverted repeats (making them direct repeats). It is possible that the inverted repeats help stabilize the rest of the chloroplast genome, as chloroplast DNAs which have lost some of the inverted repeat segments tend to get rearranged more.


title: Chloroplast

text: New chloroplasts may contain up to 100 copies of their DNA, though the number of chloroplast DNA copies decreases to about 15–20 as the chloroplasts age. They are usually packed into nucleoids, which can contain several identical chloroplast DNA rings. Many nucleoids can be found in each chloroplast.


title: Chloroplast

text: In primitive red algae, the chloroplast DNA nucleoids are clustered in the center of the chloroplast, while in green plants and green algae, the nucleoids are dispersed throughout the stroma.


title: Chloroplast

text: Though chloroplast DNA is not associated with true histones, in red algae, similar proteins that tightly pack each chloroplast DNA ring into a nucleoid have been found.


title: Chloroplast

text: In chloroplasts of the moss "Physcomitrella patens", the DNA mismatch repair protein Msh1 interacts with the recombinational repair proteins RecA and RecG to maintain chloroplast genome stability. In chloroplasts of the plant "Arabidopsis thaliana" the RecA protein maintains the integrity of the chloroplast's DNA by a process that likely involves the recombinational repair of DNA damage.


title: Chloroplast

text: The mechanism for chloroplast DNA (cpDNA) replication has not been conclusively determined, but two main models have been proposed. Scientists have attempted to observe chloroplast replication via electron microscopy since the 1970s. The results of the microscopy experiments led to the idea that chloroplast DNA replicates using a double displacement loop (D-loop). As the D-loop moves through the circular DNA, it adopts a theta intermediary form, also known as a Cairns replication intermediate, and completes replication with a rolling circle mechanism. Transcription starts at specific points of origin. Multiple replication forks open up, allowing replication machinery to transcribe the DNA. As replication continues, the forks grow and eventually converge. The new cpDNA structures separate, creating daughter cpDNA chromosomes.


title: Chloroplast

text: In addition to the early microscopy experiments, this model is also supported by the amounts of deamination seen in cpDNA. Deamination occurs when an amino group is lost and is a mutation that often results in base changes. When adenine is deaminated, it becomes hypoxanthine. Hypoxanthine can bind to cytosine, and when the XC base pair is replicated, it becomes a GC (thus, an A → G base change).


title: Chloroplast

text: In cpDNA, there are several A → G deamination gradients. DNA becomes susceptible to deamination events when it is single stranded. When replication forks form, the strand not being copied is single stranded, and thus at risk for A → G deamination. Therefore, gradients in deamination indicate that replication forks were most likely present and the direction that they initially opened (the highest gradient is most likely nearest the start site because it was single stranded for the longest amount of time). This mechanism is still the leading theory today; however, a second theory suggests that most cpDNA is actually linear and replicates through homologous recombination. It further contends that only a minority of the genetic material is kept in circular chromosomes while the rest is in branched, linear, or other complex structures.


title: Chloroplast

text: One of competing model for cpDNA replication asserts that most cpDNA is linear and participates in homologous recombination and replication structures similar to the linear and circular DNA structures of bacteriophage T4. It has been established that some plants have linear cpDNA, such as maize, and that more species still contain complex structures that scientists do not yet understand. When the original experiments on cpDNA were performed, scientists did notice linear structures; however, they attributed these linear forms to broken circles. If the branched and complex structures seen in cpDNA experiments are real and not artifacts of concatenated circular DNA or broken circles, then a D-loop mechanism of replication is insufficient to explain how those structures would replicate. At the same time, homologous recombination does not expand the multiple A --> G gradients seen in plastomes. Because of the failure to explain the deamination gradient as well as the numerous plant species that have been shown to have circular cpDNA, the predominant theory continues to hold that most cpDNA is circular and most likely replicates via a D loop mechanism.


title: Chloroplast

text: The chloroplast genome most commonly includes around 100 genes that code for a variety of things, mostly to do with the protein pipeline and photosynthesis. As in prokaryotes, genes in chloroplast DNA are organized into operons. Unlike prokaryotic DNA molecules, chloroplast DNA molecules contain introns (plant mitochondrial DNAs do too, but not human mtDNAs).


title: Chloroplast

text: Over time, many parts of the chloroplast genome were transferred to the nuclear genome of the host, a process called "endosymbiotic gene transfer". As a result, the chloroplast genome is heavily reduced compared to that of free-living cyanobacteria. Chloroplasts may contain 60–100 genes whereas cyanobacteria often have more than 1500 genes in their genome. Recently, a plastid without a genome was found, demonstrating chloroplasts can lose their genome during endosymbiotic the gene transfer process.


title: Chloroplast

text: Endosymbiotic gene transfer is how we know about the lost chloroplasts in many CASH lineages. Even if a chloroplast is eventually lost, the genes it donated to the former host's nucleus persist, providing evidence for the lost chloroplast's existence. For example, while diatoms (a heterokontophyte) now have a red algal derived chloroplast, the presence of many green algal genes in the diatom nucleus provide evidence that the diatom ancestor had a green algal derived chloroplast at some point, which was subsequently replaced by the red chloroplast.


title: Chloroplast

text: In land plants, some 11–14% of the DNA in their nuclei can be traced back to the chloroplast, up to 18% in "Arabidopsis", corresponding to about 4,500 protein-coding genes. There have been a few recent transfers of genes from the chloroplast DNA to the nuclear genome in land plants.


title: Chloroplast

text: Of the approximately 3000 proteins found in chloroplasts, some 95% of them are encoded by nuclear genes. Many of the chloroplast's protein complexes consist of subunits from both the chloroplast genome and the host's nuclear genome. As a result, protein synthesis must be coordinated between the chloroplast and the nucleus. The chloroplast is mostly under nuclear control, though chloroplasts can also give out signals regulating gene expression in the nucleus, called "retrograde signaling".


title: Chloroplast

text: Protein synthesis within chloroplasts relies on two RNA polymerases. One is coded by the chloroplast DNA, the other is of nuclear origin. The two RNA polymerases may recognize and bind to different kinds of promoters within the chloroplast genome. The ribosomes in chloroplasts are similar to bacterial ribosomes.


title: Chloroplast

text: Because so many chloroplast genes have been moved to the nucleus, many proteins that would originally have been translated in the chloroplast are now synthesized in the cytoplasm of the plant cell. These proteins must be directed back to the chloroplast, and imported through at least two chloroplast membranes.


title: Chloroplast

text: Curiously, around half of the protein products of transferred genes aren't even targeted back to the chloroplast. Many became exaptations, taking on new functions like participating in cell division, protein routing, and even disease resistance. A few chloroplast genes found new homes in the mitochondrial genome—most became nonfunctional pseudogenes, though a few tRNA genes still work in the mitochondrion. Some transferred chloroplast DNA protein products get directed to the secretory pathway, though many secondary plastids are bounded by an outermost membrane derived from the host's cell membrane, and therefore topologically outside of the cell because to reach the chloroplast from the cytosol, the cell membrane must be crossed, which signifies entrance into the extracellular space. In those cases, chloroplast-targeted proteins do initially travel along the secretory pathway.


title: Chloroplast

text: Because the cell acquiring a chloroplast already had mitochondria (and peroxisomes, and a cell membrane for secretion), the new chloroplast host had to develop a unique protein targeting system to avoid having chloroplast proteins being sent to the wrong organelle.


title: Chloroplast

text: In most, but not all cases, nuclear-encoded chloroplast proteins are translated with a "cleavable transit peptide" that's added to the N-terminus of the protein precursor. Sometimes the transit sequence is found on the C-terminus of the protein, or within the functional part of the protein.


title: Chloroplast

text: After a chloroplast polypeptide is synthesized on a ribosome in the cytosol, an enzyme specific to chloroplast proteins phosphorylates, or adds a phosphate group to many (but not all) of them in their transit sequences.


title: Chloroplast

text: Phosphorylation helps many proteins bind the polypeptide, keeping it from folding prematurely. This is important because it prevents chloroplast proteins from assuming their active form and carrying out their chloroplast functions in the wrong place—the cytosol. At the same time, they have to keep just enough shape so that they can be recognized by the chloroplast. These proteins also help the polypeptide get imported into the chloroplast.


title: Chloroplast

text: From here, chloroplast proteins bound for the stroma must pass through two protein complexes—the TOC complex, or "translocon on the outer chloroplast membrane", and the TIC translocon, or "translocon on the inner chloroplast membrane translocon". Chloroplast polypeptide chains probably often travel through the two complexes at the same time, but the TIC complex can also retrieve preproteins lost in the intermembrane space.


title: Chloroplast

text: In land plants, chloroplasts are generally lens-shaped, 3–10 μm in diameter and 1–3 μm thick. Corn seedling chloroplasts are ≈20 µm in volume. Greater diversity in chloroplast shapes exists among the algae, which often contain a single chloroplast that can be shaped like a net (e.g., "Oedogonium"), a cup (e.g., "Chlamydomonas"), a ribbon-like spiral around the edges of the cell (e.g., "Spirogyra"), or slightly twisted bands at the cell edges (e.g., "Sirogonium"). Some algae have two chloroplasts in each cell; they are star-shaped in "Zygnema", or may follow the shape of half the cell in order Desmidiales. In some algae, the chloroplast takes up most of the cell, with pockets for the nucleus and other organelles, for example, some species of "Chlorella" have a cup-shaped chloroplast that occupies much of the cell.