Can the Lyon hypothesis be tested in a human female who is homozy...

Question

Can the Lyon hypothesis be tested in a human female who is homozygous for one allele of the X-linked G6PD gene? Why, or why not?

Accepted Answer

Hi, everyone. Let's look at our next problem. It says because it is encoded by the blank gene, glucose, six phosphate dehydrogenase deficiency is more common in men than in women. Well, when we look at our answer choices, so we have a dominant, excellent, dominant, excellent recessive and Y linked, we can go ahead and eliminate some of these right away. We can eliminate choice a autosomal dominant because autosomal genes would not be more common in men than in women. There's no reason why there would be a difference there. We can also eliminate choice d why linked, um why linked traits would only occur in men? They wouldn't occur at all in women. So you wouldn't say they're more common in men than women. They just wouldn't occur in women. So we're down to excellent, dominant and excellent recessive. Well, an excellent dominant trait should be equally occurring because an individual only needs one copy of the gene to be affected by the condition. So there, it wouldn't make a difference whether you had one X chromosome or two. Since all you need is one copy. So we're looking at choice C linked recessive as our correct answer because you need two copies of the gene to express the condition. Um if you have two X chromosomes, but where men have only a single X chromosome, uh they only need one copy to express the condition. So that will result in many more men than women carrying the condition. Since they only need to inherit one copy from a parent to express it, a woman would need to either inherit um be homozygous for the condition inherit the gene from both parents, which will be a much less likely event um or to have an inactivation of one of her X chromosomes. Again, a much more rare event. So the glucose six phosphate, the hydrogenous deficiency um which is more common in men than in women is choice C carried on the ex linked rec carried by the ex linked recessive gene. See you in the next video.

Can the Lyon hypothesis be tested in a human female who is homozygous for one allele of the X-linked G6PD gene? Why, or why not?

Key Concepts

Lyon Hypothesis

X-linked Inheritance

Homozygosity in X-linked Genes

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