AGB 121: Principles of Animal Genetics and Population Genetics (2+1)

DISPERSIVE PROCESS

• Dispersive process differs from systematic processes in being random in direction and predictable only in amount.
• If systematic factors were present, as in very large population, gene frequencies would reach equilibrium and remain there until external conditions change.
• This property of stability does not hold in small populations and the gene frequencies are subject to random fluctuations arising from sampling of gametes.
• The gametes that transmit genes to the next generation carry a sample of the genes in the parent generation.
• If the sample is not large, the gene frequencies are liable to change from one generation to the next.

Causes

• Small population size
• Founder effects – occurs when a population is initially established by small number of breeding individuals
• Bottleneck effect – occurs when a population is dramatically reduced in size

Effects

• Random drift
• Differentiation between sub-populations
• Uniformity within sub-populations
• Increased homozygosity