Allele frequency — Science definition
How common a particular allele is in a population's gene pool, usually written as a fraction or percentage of all copies of that gene.
Where it is taught
- Speciation & Mechanisms of Evolution — Evolution, Ancestry & Biodiversity, Life Science: Biology, Grade 10
Questions using allele frequency
Problem 1
A population of 800 individuals has the A allele at a frequency of 0.25. A bottleneck event reduces the population to just 40 survivors, and by chance the A allele frequency in the survivors is now 0.60. Each individual is diploid and carries 2 copies of the gene. How many copies of the A allele are present in the 40 survivors?
Answer and explanation
48 copies
40 survivors x 2 copies each = 80 total gene copies. 0.60 x 80 = 48 copies of the A allele.
Problem 2
Distinguish genetic drift from natural selection as causes of a change in allele frequency.
Answer and explanation
Natural selection changes frequencies because particular heritable variants raise their bearers' reproductive success, so the change is related to the alleles' effects. Genetic drift changes frequencies through chance in which individuals happen to reproduce, so the change is unrelated to the alleles' effects and can even reduce the frequency of a beneficial allele. Both alter populations, but only selection produces a consistent relationship between an allele's effect and its fate.
Response criteria
- State a biologically accurate conclusion.
- Show the data, mechanism, or calculation that supports it.
- Include units, conditions, or limits where relevant.