pedigrees :(

I'm going to have to say A, since D seems likely but shows how the father passes it down to sons, but we want to see how the MOTHER passes the trait down to sons.

Post Merge: 11 years ago

To clarify, the mother is the carrier for the allele that brings about the expression of the trait, so she has to pass down that one allele to her son. If she were to pass it onto her daughter, then the daughter would be a carrier, not actually expressing the gene unless her father is expressing the gene and therefore passes his X chromosome with the allele onto her, making her homozygous for that trait. The sons are just HEMIZYGOUS for that trait, and express that trait fully if they carry the allele for it. So, the mother is a normal carrier and she passes it onto her daughters (with a normal husband) and they are carriers, but her sons actually express the trait.

yeah i was thinking A but got confused. thanks for helping!

You're welcome!