00:01
In birds, brown feathers are dominant over grey.
00:04
Yellow legs are dominant over white.
00:06
Okay, so i'm going to label these genes.
00:09
We're going to say that capital b is for brown feathers, and little b is for grey.
00:18
And we'll say capital y is for yellow legs, little y is for white.
00:24
Totally arbitrary, pick whatever letters you want, as long as you give the capital letter to the dominant rate and the lowercase to the recessive.
00:30
It makes it easier to do the rest of the question.
00:33
Now, looking at these two parents, the male bird is heterozygous, the brown, so he gets one of each, the 15, and he has white legs.
00:44
He has a recessive trait, so he has two copies of the recessive allele.
00:50
Female has homozygous, brown feathers.
00:53
Homozygous means two of the same, and she's heterozygous, the leg colour.
00:59
Let's do this cross.
01:00
So the first step of any cross is to make sure you get the parental genotypes.
01:05
So that's why i've labelled the genes and i've written out the parental genotypes.
01:10
This we're going to do a cross.
01:11
We'll do a punnet square, but we won't dive in and do a big 4x4...