00:01
A homozygous dominant female has kids with a male that has dmd.
00:06
So that's duchenne muscular dystrophy.
00:08
It's an x -linked disorder.
00:10
So you could have x with a capital d, which is the normal allele, or x with a little d, which is dmd.
00:19
It's a recessive condition.
00:22
So a homozygous dominant female has kids with a male who has the condition.
00:26
So the female has two copies of the normal allele.
00:31
The male only gets one x chromosome and it has the recessive harmful alliole.
00:39
So this is the cross that we're doing for question 1.
00:42
First step of any cross is to work out the parental genotypes.
00:46
Second step is we're going to do a punnet square.
00:51
So in a punnet square, we put the parental alleles on the outside, and then we combine them, get all of the possibilities.
01:10
So each offspring gets one allele from each parent.
01:14
Okay, so 1a is what percentage will be female carriers.
01:22
So how many squares here are for female carriers? what is these two squares here? both of these are female, they have two x chromosomes, and they have one of each.
01:34
So these are the carriers.
01:36
So 1a is going to be 50%.
01:42
One b is what is the chance these two parents will have a child with the condition.
01:48
Well, how many of these squares have the condition? none of them...