Question

If the first child of a couple was without dimples, an recessive trait, what is the chance that the second child will be born without dimples?
A) 100%
B) 25%
C) 50%
D) Cannot be determined from the phenotype of the child

Answer 1

If dimples (d) is a recessive trait to non-dimples (N), then each parent could be NN or Nd. If one or both NN, P(N) = 100%. If both Nd, then P(N) = 75%. Thus it cannot be determined from the phenotype of the first child.