Purple pea flowers are dominant over white. A cross of two purple plants has produced a white offspring. What is the probability their third offspring is purple, to 2 decimals?
A white offspring is pp, so both purple parents must carry p: the cross is Pp × Pp. Its offspring probabilities are 1/4 PP, 1/2 Pp, 1/4 pp. Purple therefore has probability 3/4 = 0.75. Previous offspring establish parental genotype but do not alter the independent probability for the third.