In the fruit fly Drosophila, eye color is an X-linked trait,…

In the fruit fly Drosophila, eye color is an X-linked trait, with the allele for red (R) dominant to the allele for white (r).  Which of the following is true of a cross in which the P generation is a white-eyed female crossed with a red-eyed male.  Feel free to use scratch paper.

Tay-Sachs disease is a rare recessive autosomal disease.  Ja…

Tay-Sachs disease is a rare recessive autosomal disease.  Jacob & Sarah are married and have a daughter.  None of the three of them have the disease, but both Jacob’s mother and Sarah’s father did have the disease. What is the probability that the couple’s daughter is a carrier for Tay-Sachs (i.e. heterozygous at the T-S locus)?  (Draw a pedigree on scratch paper if you wish, then select your answer from the choices below.)