A woman, S.R., had a maternal grandfather with hemophili...

Question

A woman, S.R., had a maternal grandfather with hemophilia A (OMIM 306700), an X-linked recessive condition that reduces blood clotting. S.R.'s maternal grandmother and paternal grandparents are free of the condition, as are her partner, his parents, and his grandparents. S.R. has no siblings. She wants to know the chance that a son of hers will have the condition. What is that probability?

Accepted Answer

Hello, everyone and welcome to today's video. So the following conditions can be caused by an autosomal dominant inheritance except as answer choice. A we have Huntington's disease as answer choice. B we have morphine syndrome. C is hemophilia, D is achondroplasia. Now, in order to solve this problem, let's understand out dominant inheritance. Well, for example, let's say we have a female. We say that a disease has an auto so dominant inheritance when only one copy of a mutated gene is enough to express or cause a person to have the disease. Now, Huntington's disease syndrome and an achondroplasia, all are considered autosomal dominant diseases because only one copy of these are going to cause a person to express the disease. And therefore we're going to cancel them out. Now, when it comes to hemophilia, let's look at a female again. So females are going to have two X chromosomes. Hemophilia is required to be present in both of the X chromosomes for the female to express the hemophilia disease. Now, if it's only present in one, she will not express it. And this makes emo hemophilia an X linked recessive disease, which is not out of. So dominant. And because of this, we're going to highlight answer choice c hemophilia as the final answer to this question. I really hope it's helped and I hope to see you on the next video.

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