00:01
We're looking at a population of turtles in hardy -weinberg equilibrium.
00:04
There are two alleles for shell colour.
00:07
F, which is dominant, gives brown shells.
00:10
Little f gives yellow shells.
00:13
Okay, so there are three genotypes here.
00:17
You can have two copies of the brown shell allele.
00:20
One of each, the heterozygote, or two of the recessive.
00:25
Okay, 64 % have brown shells.
00:30
We want to work out how many are homozygote.
00:32
Dominance, how many are heterozygous? how do we do this? okay, so at hardy -wyneberg equilibrium, there are two equations you need to know.
00:41
First one looks like this, and this is allele frequency.
00:47
Every copy of the shell -colour gene is either the dominant, brown, or the recessive yellow.
00:52
So if you guys at their frequencies, you'll get 100%.
00:55
The second equation looks like this.
01:02
Okay, so these represent the three possible genotypes, and their frequencies are also.
01:07
Going to add up to 100%, because every turtle is one of those three genotypes.
01:14
And we have been given the frequency of brown shells.
01:17
Well, because this is the dominant rate, both the homozygous dominant and the heterozygous turtles have brown shells.
01:24
So this is 0 .64.
01:27
Where do we go from here? well, we can't do much here because we have two variables, the two allele frequencies, and only one equation.
01:35
F squared plus 2 big f little f equals 0 .64.
01:39
So instead, we're going to look at this bit here.
01:43
So if this is 0 .64, this has to be 0 .36.
01:51
This we can work with, because now we have a single variable.
01:54
We have little f squared equals 0 .36.
01:57
And at equilibrium, little f squared isn't just a representation...