Below is a pedigree for a neurological disease. The son is affected (solid squar

Question

Below is a pedigree for a neurological disease. The son is affected (solid square).

The mother becomes pregnant again. Amniocentesis shows that the fetus has a Y chromosome. The parents want to know whether the child will be affected. You conduct a PCR analysis of the disease gene of cells from the fetus. What are the possible results, and what will you tell the parents?

** I know that If the child has the 300 base pair product, he will not be affected. If he has the 330 base pair product, he will be affected. But please explain more in depth.

Explanation / Answer

From the data given above, the pedigree is insufficient to determine whether the neurological disease is X-linked, autosomal recessive or autosomal dominant.

All that can be stated is that it is not Y-linked as the father is not affected.

But the disease being one of either the above three other scenarios, there is a 50% chance of the second son being affected or not.

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