Honor System


Course Topics


Homework Assignment - Population Genetics

100 points total

Use complete sentences (where appropriate) for all of your answers. If you are stumped by a problem, explain as much as you can to get partial credit.

1. What are the differences between speciation via anagenesis and cladogenesis? (10 points)

2. In corn, salmon colored silks and shrunken endosperm are controlled by a recessive alleles, sm and sh, respectively. The two genes assort independently. A sample from a random mating population was collected and the following distribution was noted. (10 points)

Phenotype Number
Shrunken 6
Salmon Shrunken 10
Salmon 54
Wild Type 30
Total 100

Determine the frequencies of each allele at both genes in this corn population.

3. RFLP mapping at a specific locus in Colorado Columbine (a plant found in the Rocky Mountains) demonstrated that two alleles were present. One allele (A1) represents a 5.0 kb band and the second allele (A2) represents a 4.0 kb band. A sample of plant s was collected in the Rocky Mountain National Park, and 135 were scored as genotype A1A1, 1,530 were genotype A1A2 and 4,335 were A2A2. What are the allelic frequencies of A1 and A2 in this population? (10 points)

4. Below are ten populations, and the proportion of each genotype in each populationis given.

Population AA Aa aa
1 1.0 0.0 0.0
2 0.0 1.0 0.0
3 0.0 0.0 1.0
4 0.5 0.25 0.25
5 0.25 0.25 0.5
6 0.25 0.5 0.25
7 0.33 0.33 0.33
8 0.04 0.32 0.64
9 0.64 0.32 0.04
10 0.986049 0.013902 0.000049

a. What are the allelic frequencies for the A and a alleles in each population? (10 points)
b. Which populations are in Hardy-Weinberg equilibrium? (10 points)

5. Your research group consists of population geneticists collaborating with a large research team that is studying cystic fibrosis. The molecular geneticists on the team discovered that most cases of cystic fibrosis are caused by a 3 base pair deletion of the gene which results in a deletion of the phenylalanine residue at position 508 of the functional protein. The applied molecular geneticists on the team developed a PCR screening technique that took advantage of this deletion. This technique accurately detects those individuals homozygous for the deletion and therefore at risk for cystic fibrosis.

A large collection of blood samples were collected and analyzed from different ethnic groups from throughout the world. The results of this screening were returned, and your group determined the frequency of individuals homozygous for the phenylalanine 508 deletion among different groups (See table below).
Ethnic Group Frequency
Northern and Central Europe 1/2,500
Hispanic 1/8,500
Aftrican 1/14,000
Asian 1/89,000

The data clearly shows that for most groups the frequency of individuals with a strong predisposition to the disease is relatively low. Yet your are aware that the frequency of carriers of the CF allele must also be calculated for each ethnic group because that is important in the maintenance of the disease in the population. Calculate the carrier frequency for each population. (10 points)

You recently read about a new religious colony that was formed by 25 couples of Northern European ancestry and 25 couples from Hispanic ancestry. The formation of this colony raises several intriguing population genetics questions.

What is the frequency of the carriers of the CF allele in the new colony? (10 points)

What will be the frequency of the CF and normal alleles among the next generation of children within this colony? (10 points)

If the children from the founders only mate with other children from the colony what will be the frequency of the two alleles? (10 points)

As is often the case, other individuals will enter the colony in the future. If members of the colony mate with individuals of African or Asian ancestry, what effect will it have on the frequencies of the two alleles? (10 points)