Assume that in the F2 of a series of crosses, 1/64 of the offspring resemble one
ID: 80805 • Letter: A
Question
Assume that in the F2 of a series of crosses, 1/64 of the offspring resemble one of the parents (P). How many gene pairs are involved in producing these results?
Answer: three
Assume that four polygenic gene pairs are involved in determining phenotypes of F2. How many phenotypic classes are expected?
Answer: nine
Assume that you are studying a trait determined by a number of polygenes. If there are seven phenotypic categories, how many genes are probably involved?
Answer: three gene pairs
***These are all questions/answers from a study sheet. Im trying to understand how these answers were reached, please show work, thanks.
Explanation / Answer
Ans 1.
1 / 4n = Ratio of f2 individuals showing extreme phenotype = 1 / 64 in this problem
Therefore 4n = 64
n = 3
Ans 2. If N is no. of phenotypic classes, and n is the number of polygenic pairs, then N = 2n + 1
In this problem , n = 4, So N = 2 (4) + 1 = 8 + 1 = 9
Ans 3. Same formula as above, N = 7, so 7 = 2n + 1 . Hence 2n = 6 , n = 3. i.e 3 gene pairs.