Duchenne muscular dystrophy a genetic disorder that impairs...

Duchenne muscular dystrophy, a genetic disorder that impairs muscle function, is a sex-linked recessive trait carried on the X chromosome. Suppose a man who does not suffer from muscular dystrophy marries a woman who is a carrier for the condition. If they have a boy, what are the chances he will inherit muscular dystrophy? Question 31 options: 100% 0% 75% 50%

Transcript

00:01 So, in the question, a few of the mcqs have been given, okay.

00:04 The first question says that for muscular dystrophy, which is a sex -linked recessive trait, a normal male and a carrier female was crossed.

00:14 So, we have individual, the first one is a normal male and this male is crossed with a carrier female and as a resultant, what they have asked that and they have a male child, okay, with that condition.

00:31 So that means that this male child have muscular dystrophy, alright.

00:37 So, the first question is what is the chance that the next child has the muscular dystrophy regardless of the gender.

00:45 So, what we know that it is a sex -linked recessive trait, okay.

00:49 So the normal, for the normal male, the genotype is xy and for the female, okay, the genotype is xx and since she is a carrier, that means one of the x contains the gene for muscular dystrophy.

01:06 So, we are putting m here, right.

01:08 So if we are crossing them, okay, let's draw the checkerboard here.

01:13 So, we have x and then xm.

01:17 So what we see, xx, then xxm, we have xy and we have xmy, right.

01:26 So, among these, what are the chances that the next child will have the disease? so only this child will have the disease, right.

01:36 We already know that this male child had the disease, okay.

01:40 So here is xmy, the genotype for this particular male child...

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