Allele frequency
Allele frequency or natural frequency is a concept of population genetics, which describes the relative frequency of copies of an allele in a population. The gene frequency is calculated by dividing by the total number of copies of all alleles that are present in the population of the number of copies of a particular allele.
Differential gene frequencies in a population indicate genetic diversity because they allow many alleles. High gene frequencies allow less alleles.
Evolution takes place when changes the gene frequency of a population. Possible causes of this are natural selection ( increasing the gene frequency of individual alleles ) or genetic drift.
Example
Consider a population consisting of ten diploid individuals. For a particular gene, there are two alleles: A and a Judging from the following genotypes from:
AA, AA, AA, AA, AA, AA, aa, aa, aa, aa
Then the gene frequency of allele AP (A) and for allele a P (a) is calculated as:
- P (A) = (2 2 2 2 2 2): 20 = 0.6
- P (a) = (2 2 2 2): 20 = 0.4
For the following genotypes:
AA, AA, Aa, Aa, Aa, Aa, Aa, Aa, Aa, Aa
One obtains:
- P (A) = ( 2 2 1 1 1 1 1 1 1 1): 20 = 0.6
- P (a) = (1 1 1 1 1 1 1 1): 20 = 0.4
General rule: P (A ) P (a ) = 1 ( complementarity of all alleles, here: A and a)
The gene frequency is independent of the distribution of alleles in the gene pool of the population.
Without a knowledge of the mating system and present Genkopplungen generally obtained no injective mapping of the set of gene frequencies on quantity of the genotype frequencies.