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## Allele frequency
Given the following: - a particular locus on a chromosome and the gene occupying that locus
- a population of individuals carrying
*n*loci in each of their somatic cells (e.g. two loci in the cells of diploid species, which contain two sets of chromosomes) - variants or alleles of the gene exist,
then the allele frequency is the fraction or percentage of times that a given allele is present at a locus within the population. For example, if the frequency of an allele is 20% in a given population, then among population members, one in five chromosomes will carry that allele. Four out of five will be occupied by other variant(s) of the gene. Note that for diploid genes the fraction of individuals that carry this allele may be nearly The frequencies of all the alleles of a given gene often are graphed together as an ## Additional recommended knowledge
## Calculation of allele frequencies from genotype frequenciesIf - frequency of A
Similarly, the frequency - frequency of a
It would be expected that and from this we get: *q*= 1 −*p*and*p*= 1 −*q*
If there are more than two different allelic forms, the frequency for each allele is simply the frequency of its homozygote plus half the sum of the frequencies for all the heterozygotes in which it appears.
Allele frequency can always be calculated from genotype frequency, whereas the reverse requires that the Hardy-Weinberg conditions of random mating apply. This is partly due to the ## An example populationConsider a population of ten individuals and a given locus with two possible alleles, *AA*,*Aa*,*AA*,*aa*,*Aa*,*AA*,*AA*,*Aa*,*Aa*, and*AA*
Then the allele frequencies of allele so if an individual is chosen at random there is a 70% chance it will carry that allele and there is a 30% chance that an individual chosen at random will have the a-allele ## The effect of mutationLet ù be the mutation rate from allele A to some other allele a ( the probability that a copy of gene A will become a during the DNA replication preceding meiosis). If
where
## See alsoCheung, KH; Osier MV, Kidd JR, Pakstis AJ, Miller PL, Kidd KK (2000). "ALFRED: an allele frequency database for diverse populations and DNA polymorphisms".
Categories: Population genetics | Genetic genealogy |
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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Allele_frequency". A list of authors is available in Wikipedia. |