00:02
Hi there.
00:02
In this question, we are trying to determine the genotypes of some individuals based upon what we see expressed in their phenotypes.
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So we have sam.
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So we're going to draw, we're going to put together a pedigree.
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And in a pedigree, boxes stand for males and circles are females.
00:34
If a person has hemophilia, i will shade the box.
00:38
I'll color it in a little.
00:39
Bit.
00:40
All right.
00:40
So we have sam who has hemophilia.
00:47
So sam is the father here.
00:52
He has hemophilia.
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And then we have brenda.
01:00
And brenda does not have hemophilia.
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She's phenotypically normal.
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So this is sam here.
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And this is brenda.
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And they have a daughter who is a hemophiliac.
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So their daughter here is going to be a circle that is going to be shaded because she has hemophilia.
01:30
Okay, and we know it's an x -linked recessive.
01:35
So that means her genotype.
01:39
So i'm going to use x capital h for normal.
01:43
Sex -length means it's just carried on the x chromosome.
01:48
So x with a capital h is normal.
01:50
That is dominant over x, lowercase h.
01:54
Which is hemophilia.
02:00
All right, so back to their daughter.
02:01
She's a female, so she has to have two x chromosomes, and they both must have the allele for hemophilia, for her to be a hemophiliac, since it's a recessive trait.
02:13
Sam has hemophilia, and he's a male...