Genetic drift and gene flow (L4)

Genetic drift, what population does it most affect, two examples

A process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next

Effects are most pronounced in small populations

Two examples: founder effect and bottleneck effect

What is the consequence of genetic drift for populations? Within vs among populations

Genetic drift is expected to lead to a decrease in genetic variation WITHIN a population

Eventually, some alleles may be lost and others may become fixed

AMONG populations, genetic drift leads to an increase in genetic variation. This is because the change in allele frequency is random and populations are independent

What is gene flow

Gene flow consists of movement of alleles among populations

Alleles can be transferred through movement of fertile individuals or gametes (for example, pollen)

What are the effects of gene flow? How can it increase/decrease fitness? Among/within populations?

Gene flow can decrease the fitness of a population…

But gene flow can increase the fitness of a population through local adaptation, as it increases genetic variation which can lead to the spread of beneficial alleles

Gene flow can lead to increased genetic variation WITHIN populations

Gene flow can lead to decreased differences in the allele composition BETWEEN populations