Sunday, September 23, 2012
Science Sundays: Dishing on Genetic Drift
Welcome back to Science Sundays :) Today I thought I'd hit on another genetic concept that I've been hitting home with my students all week (well, at least attempting to). Genetic Drift: sounds cool, right? It is a powerful force, and would have a big effect if, say you had a new population being founded, or lost a huge chunk of a population.
That new population that was founded on Mars or the moon? They might have some issues with genetic drift.
This skew from the actual total variability and range in a population in each sample that's taken can work from generation to generation. Just by chance (sampling error) not all the variability that exists in a population may get passed down from one generation to the next. Say someone with a unique gene variant (allele) doesn't have children, or doesn't pass along that specific allele: well, then it's lost. Over time, just through random chance, genetic drift works to get rid of variability in a population. A population will eventually hit what is known as fixation, where they've lost all the variability for a gene. It's crazy how this happens, but drift is one of those forces that is totally random and therefore super powerful.
Okay, so the true interesting stuff that happens is when genetic drift principles are applied to founding a new population. This is where Founders Effect comes into play. Simply, it's where a new population in formed and brings with it a random sample of the variability in the parent population. What usually happens is that variability is lost this way, as the migrants take less variation with them as they pick up and leave.
This has turned into a giant post, but hopefully it makes sense. Anyone have a good example of genetic drift they want to share?