00:01
We're looking at a population of butterflies.
00:03
There are two alliotes, capital b and capital g.
00:08
The frequency of b is nought .3.
00:11
So this is the information we have going in.
00:13
We want to know how many green -winged butterflies are going to be, and green is recessive.
00:19
So there are three genotypes, because each butterfly has two copies of a gene.
00:24
So there's two copies of b, there's one of each, and there's two copies of g.
00:35
Now, we're told that g is recessive, so the green -winged butterflies, ones we're looking at, are only going to be this group here.
00:44
So how do we work this out? well, we're told it's in hardy -weinberg equilibrium.
00:48
When you see that there are two equations, you should write out.
00:52
The first one is adding up your two alleles to get one.
00:57
So each copy of the gene is one of these two allions, blue or green, which means if you add up their frequencies, you'll get 100%.
01:04
From here, we immediately know the frequency of the green allele.
01:09
So this is going to be 0 .7.
01:12
The second equation is this.
01:17
So b squared plus 2bg plus g squared equals 1.
01:28
Okay, so this second equation is for genotype frequency...