How does genetic drift affect gene frequencies?

Question

How does genetic drift affect gene frequencies?

Answer 1

Genetic Drift can be defined as "A mechanism for evolutionary change resulting form the random fluctuations of gene frequencies from one generation to the next." (Relethford p.84)

One of the best ways to understand genetic drift is to look at - founder effect.   This is a type of genetic drift where upon a small population form a new genetic pool off from the group.  The frequencies of certain gene will increase or decrease relative to the group.  With out gene flow - or the flow of genes between populations - can cause particular traits to be found common within a people do to their ancestors limited mating populations.

A disease, for example, like Tay-Sachs is found in Ashkenazim Jewish populations, most likely due to genetic drift. (Diamond p.59)  Here is where you find explanations about fatal disorders being advantages to some degree or they would not be passed along.  To understand more I would read  - Curse and Blessing of the Ghetto by Jared Diamond - and - Unfortunate Drift by Josie Glausiusz.  Good Luck

Answer 2

Well theres the bottleneck effect where a catastrophe happens and only a few survive...and the allele frequency of that small survival group is different than that of the original population. Genetic drift can also occur when a few individuals leave a larger population and occupy a new habitat. All in all it usually involves a change in gene frequencies because the new population does not have the same frequency as the original.