Which of the following pairs of parents is most likely to...

Which of the following pairs of parents is most likely to produce a daughter with hemophilia? A. a carrier mother and an unaffected father B. a hemophiliac mother and an unaffected father C. An unaffected, non-carrier mother and a hemophiliac father D. a carrier mother and a hemophiliac father

Transcript

00:01 Which of these couples has the highest chance of producing a daughter with hemophilia? okay, so to start off, hemophilia is x -linked.

00:12 So that's going to be the inheritance pattern we're looking at.

00:15 For a daughter to have hemophilia, she needs both of her x chromosomes to have the allele of the hemophilia.

00:22 If she only has one, she's an unaffected carrier.

00:25 Okay, so what i'm going to do is i'm going to have the four couples, and i'm going to start by writing out what their potential of spring can have as far as sex chromosomes go.

00:40 So let's start with a.

00:41 I'm going to use black for the normal and x for the infiliate x chromosome.

00:47 So a carrier mother and an unaffected father.

00:50 So father's just going to be x, y.

00:52 The mother is going to have x.

00:57 X.

00:59 So this is the cross.

01:01 So what does this look like? if we look at the potential offspring, we have xy, we have xy, we have xy, we have x, x, x, oops, this should be a red one, and xx, okay, so i've, we've got two where they get the faulty x from the mother, and two where they don't, and then the usual combinations.

01:33 So what possibilities do we have? we have a healthy son, hemophiliac son, unaffected daughter, carrier daughter.

01:42 So those for four outcomes here, as you can see, there are no daughters with hemophilia.

01:46 So it's not going to be this answer.

01:50 So we can rule that one out, and let's go on to b.

01:52 B, we have a hemophiliac mother and an unaffected father.

01:56 So hemophiliac mother, unaffected father.

02:02 Okay, now let's look at the combinations here.

02:04 So the father can give an x chromosome, a y chromosome, but the mother can only give an affected x.

02:12 So this only has two outcomes...

Question

Which of the following pairs of parents is most likely to produce a daughter with hemophilia? A. a carrier mother and an unaffected father B. a hemophiliac mother and an unaffected father C. An unaffected, non-carrier mother and a hemophiliac father D. a carrier mother and a hemophiliac father

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