00:01
Cystic fibrosis is an inherited disease caused by a recessive allele.
00:05
So we have capital c for the normal and little c for cystic fibrosis.
00:14
Because we give the little one to the recessive trait.
00:18
A woman and her husband are both carriers.
00:21
What is the probability the child will have cystic fibrosis? so both of them have this genotype.
00:28
They have one copy of the normal allele.
00:30
And because normal is dominant, that means neither of them actually have cystic fibrosis themselves, but they both carry a recessive allele.
00:39
Okay, so let's do a punnet square, and we'll see what the outcomes might be here.
00:44
So in a punnette square, we have the parental alleles on the outside of the square, like so.
00:49
And then inside the square, we combine these to see what the offspring might inherit...