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Genetics (from the Greek genno γεννώ= give birth) is the science of genes, heredity, and the variation of organisms. The word genetics was first applied to describe the study of inheritance and the science of variation by English scientist William Bateson in a letter to Adam Sedgewick, dated April 18, 1905.

Humans began applying knowledge of genetics in prehistory with the domestication and breeding of plants and animals. In modern research, genetics provides important tools in the investigation of the function of a particular gene, e.g. analysis of genetic interactions. Within organisms, genetic information generally is carried in chromosomes, where it is represented in the chemical structure of particular DNA molecules.

Genes encode the information necessary for synthesizing proteins, which, in turn play a large role in influencing, although, in many instances, do not completely determine, the final phenotype of the organism. The phrase to code for is often used to mean a gene contains the instructions on how to build a particular protein, as in the gene codes for the protein. Note that the "one gene, one protein" concept is now known to be simplistic. For example, a single gene may produce multiple products, depending on how its transcription is regulated.



Main article: history of genetics

It was not until 1865 that Gregor Mendel first traced inheritance patterns of certain traits in pea plants and showed that they obeyed simple statistical rules. Although not all features show these patterns of Mendelian inheritance, his work acted as a proof that application of statistics to inheritance could be highly useful. Since that time many more complex forms of inheritance have been demonstrated.

From his statistical analysis Mendel defined a concept that he described as an allele, which was the fundamental unit of heredity. The term allele as Mendel used it is nearly synonymous with the term gene, whilst the term allele now means a specific variant of a particular gene.


Mendel was unaware of the physical nature of the gene. We now know that genetic information is normally carried on DNA. (Certain viruses store their genetic information in RNA). Manipulation of DNA can in turn alter the inheritance and features of various organisms.

Timeline of notable discoveries

1859 Charles Darwin publishes The Origin of Species
1865 Gregor Mendel's paper, Experiments on Plant Hybridization
1903 Chromosomes are discovered to be hereditary units
1905 British biologist William Bateson coins the term "genetics" in a letter to Adam Sedgwick
1910 Thomas Hunt Morgan shows that genes reside on chromosomes
1913 Alfred Sturtevant makes the first genetic map of a chromosome
1913 Gene maps show chromosomes containing linear arranged genes
1927 Physical changes in genes are called mutations
1931 Crossing over is the cause of recombination
1941 Edward Lawrie Tatum and George Wells Beadle show that genes code for proteins; see the original central dogma of genetics
1950 Erwin Chargaff shows that the four nucleotides are not present in nucleic acids in stable proportions, but that some general rules appear to hold (e.g., that the amount of adenine, A, tends to be equal to that of thymine, T). Barbara McClintock discovers transposons in maize
1958 The Meselson-Stahl experiment demonstrates that DNA is semiconservatively replicated
1961 The genetic code is arranged in triplets
1970 Restriction enzymes were discovered in studies of a bacterium, Haemophilius influenzae, enabling scientists to cut and paste DNA
1989 The first human gene is sequenced by Francis Collins and Lap-Chee Tsui, it encodes the CFTR protein, defects in this gene cause cystic fibrosis
1996 Saccharomyces cerevisiae is the first eukaryote genome sequence to be released
1998 The first genome sequnce for a multicellular eukaryote, C. elegans is released
2003 (14 April) Successful completion of Human Genome Project with 99% of the genome sequenced to a 99.99% accuracy [1]

Areas of genetics

Classical genetics

Main articles: Classical genetics, Mendelian inheritance

Classical genetics consists of the techniques and methodologies of genetics that predate the advent of molecular biology. After the discovery of the genetic code and such tools of cloning as restriction enzymes, the avenues of investigation open to geneticists were greatly broadened. Some classical genetic ideas have been supplanted with the mechanistic understanding brought by molecular discoveries, but many remain intact and in use, such as Mendel's laws. Patterns of inheritence still remain a useful tool for the study of genetic diseases.

Molecular genetics

Main article: Molecular genetics



Population, quantitative and ecological genetics

Main articles: Population genetics, Quantitative genetics, Ecological genetics





Main article: Genomics

A more recent development is the rise of genomics, which attempts the study of large-scale genetic patterns across the genome for (and in principle, all the DNA in) a given species. Genomics depends on the availabilty of whole genome sequences, and compuational tools developed in the field of bioinformatics for analysis of large set of data.

Closely-related fields


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