試題詳解

52. Flower color in sweet peas is controlled by two genes, C/c and E/e. C is dominant to c and E is dominant to e. A plant produces purple flowers only if it contains at least one dominant allele for each gene； otherwise it produces white flowers. If two plants heterozygous for both genes are crossed, what will be the phenotypic ratio for purple: white flowers?
(A) 3:1
(B) 4:1
(C) 9:7
(D) 5:3
(E) 15:1