00:01
Okay, so let's take a look at this problem.
00:03
There are 25 individuals in population 1, all with the genotype big a, big a, and there are 40 individuals in population 2, all with the genotype little a, little a, little a.
00:13
Assume that these populations are located far from each other, and that their environmental conditions are very similar.
00:19
Based on the information given here, the observed genetic variation most likely resulted from a, genetic drift, b, gene flow, c, non -randomating, and d, directional.
00:30
Selection.
00:32
So before we go about trying to solve this problem, let's actually figure out what it's asking for.
00:38
So it's saying that there are 25 individuals in population one with the same genotype, and there are 40 individuals in population two with the same genotype of those individuals, but a different genotype from population one.
00:51
And it's asking basically how did this observed genetic variation occur? and so these two populations with individuals are the species.
01:01
And so we can assume that they originated from the same initial population.
01:07
So there's a population before population one in population two.
01:11
And so let's draw this out where you have an initial population, right? and then this initial population, some of the individuals from the initial population broke off to a certain location and they gave rise to population one.
01:26
And then some individuals from the initial population broke off to a different location and gave rise to population two.
01:32
And so what the question is asking is how did the observed genetic variation occur between populations one and populations two? and so let's just go through the different answer choices and see which one makes the most sense.
01:47
So let's start off with option b, gene flow.
01:50
Now gene flow is basically the transfer of an allele or a genotype in between populations.
01:57
And that can be done through a variety of ways which we won't get into in this video, but the idea is that you're taking one allele from one population and you're making it prevalent in the other population.
02:09
Now, this doesn't really fit with what we see here, right, because we see that the genotypes in population one are all aa, and the genotypes in population two are all little a, little a.
02:19
There's no allele sharing here, right? the all alleals are completely different and you don't really see that there's any spread or any gene flow.
02:27
So it's not a good answer.
02:29
So let's cross that out.
02:31
Now let's go to non -random mating.
02:33
Non -random mating initially seems like a good idea, right? because then you have big a, big a being selected out.
02:39
But the key here, and the key in the textbook, is that non -random mating alone can't get changes in allele frequency, but just have changes in the frequency of homozygotes.
02:52
And so the idea basically is that if you had individuals that came from the same initial population, right? they would have big a and they would have little a...