a) 27/64 b) 37/64 c) 1/64 d) 63/64
Work Step by Step
If N=normal and n=PKU, the cross is NnxNn, and the ratio for offspring will be 1/4NN: 1/2Nn: 1/4nn. The first two listed genotypes have the normal phenotype. a) Cube the probability for any one to be normal (3/4) to get 27/64. b) This is all possible outcomes (1) minus the probability of all being normal (27/64). c) is the probability of nn cubed. d) is all possibilities (1) minus the answer in c).