Genetic Drift & Genetic bottleneck & The Founder Effect

What is genetic drift?

Genetic drift is the random change in the frequency of alleles over time.

How is there a change in frequency of alleles (in genetic drift)?

Each generation differs from the parental allele frequency, due to the random variation caused when creating gametes.

Over time, some alleles may be lost, and others increase in frequency.

Why does genetic drift affect smaller populations more?

Rare alleles are more likely to be randomly lost, decreasing the genetic diversity

What is genetic bottleneck?

A genetic bottleneck is when there is a massive reduction in the population size, i.e. through natural disaster.

This then causes a big reduction in the gene pool.

Why is a reduction in gene pool bad?

There is a decrease chance of survival from disease (as remaining genes are similar).

There is also a higher impact of genetic drift, with a more unstable population.

What is the founder effect?

A few organisms from a population start a new population, and therefore there are only a small number of different alleles from the initial gene pool.

What term describes the random change in allele frequency in a population over time?

Genetic drift

What happens with genetic drift in large and small populations?

In large populations allele frequencies tend to only vary a small amount but in small populations allele frequencies can fluctuate so much that some alleles are lost from the population.