Prometheus123

I think my class's TA may have made a mistake while writing the solutions to these problems, but is there something I'm missing? I'd appreciate clarification on confirmation on either question. 1. Albinism is a total lack of skin pigment caused by a recessive gene. What is the probability of a couple having an albino child if both are normally pigmented as are their parents, but both have albino siblings. Solution: Because they both have albino siblings, their parents were carriers, therefore the probability of both of them being carriers is (2/3)^2, and the probability for their child to be affected is (2/3)^2 × 1/4 = 1/9. My comment: The solution seems fine except for the 2/3 ratio. Shouldn't the probability of each parent being a heterozygous carrier be 2/4 = 1/2? 2. In a testcross of Aa Bb CC Dd Ee, where the genes show independent assortment, what is the expected frequency of aa bb Cc dd ee progeny? Solution: a. 1/2 × 1/2 × 1 × 1/2 × 1/2 = 1/16. My comment: Where is the little c recessive allele coming from? Why is there 100% chance that the progeny will be heterozygous Cc? Did the TA just read that Cc in the question as CC?