Allele frequency

Allele Frequency

Allele frequency, also known as gene frequency (pronunciation: /əˈliːl ˈfriːkwənsi/), is a term used in genetics to describe the relative frequency of an allele at a particular locus in a population of organisms. It is usually expressed as a proportion or a percentage.

Etymology

The term "allele frequency" is derived from the Greek word "allelon" which means "of each other", and the English word "frequency" which means "rate of occurrence". The term was first used in the early 20th century in the field of population genetics.

Definition

In a population, the allele frequency is the number of copies of a specific allele divided by the total number of all alleles for that gene in the population. It is a measure of the commonness or rarity of an allele in the population.

Calculation

The allele frequency is calculated by counting the number of times an allele appears in a population and dividing by the total number of copies of the gene. The frequency of an allele (A) is calculated as:

f(A) = (Number of copies of the allele in the population) / (Total number of all alleles for the gene in the population)

Related Terms

• Genotype frequency: The frequency of a genotype in a population.
• Gene pool: The total genetic diversity found within a population or a species.
• Hardy-Weinberg principle: A principle stating that both allele and genotype frequencies in a population remain constant from generation to generation unless specific disturbing influences are introduced.
• Genetic drift: The change in the frequency of an existing gene variant in a population due to random sampling of organisms.

See Also

• Genetic variation
• Population genetics
• Evolutionary genetics

External links

• Medical encyclopedia article on Allele frequency
• Wikipedia's article - Allele frequency

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