00:01
Ok, this question here says a couple went to see a genetic counselor because one of them has a sibling with cystic fibrosis.
00:07
So you have here the couple, ok, and in this case let's suppose that the woman has a child with or well it says that one of them has a sibling.
00:24
So let's suppose that the woman again, these are the woman's parents and she has a brother let's suppose with cystic fibrosis.
00:34
Remember that in this case we are going to use, we are using the cf plus or cf negative alleles, but let's use the a, it is simple.
00:45
So the homozygous dominant and the heterozygous are going to be normal.
00:49
The homozygous recessive is going to be for a person with cystic fibrosis, ok.
00:52
So in this case it says, cystic fibrosis is caused by homozygosity for a girl with a recessive recalcitrant disease, allele.
01:00
Neither a member of the couple nor any of their four parents is affected.
01:04
And it says what is the probability that their child will be a carrier of cystic fibrosis disease allele? so in this case, you have this man here, he is homozygous recessive and remember that the person in here is one allele from each parent.
01:18
In this case, one recessive a came from the mother and one recessive a came from the father.
01:23
So both parents must have at least one recessive a.
01:26
So they can be either homozygous recessive or heterozygous.
01:29
But it says that both of them are healthy so they are not homozygous recessive and they are heterozygous.
01:36
So both parents are heterozygous for sure.
01:39
Now they are asking you the probability for them to have a child, ok, that is a carrier.
01:46
So this condition is rare...