A maternal effect mutation bicoid (bcd) is recessive. The bcd allele makes no Bicoid protein. In the absence of the Bicoid protein, product embryogenesis is not completed and eggs fail to hatch into viable larva

Question

Consider a cross between a female who is heterozygous (bcd+/bcd) and a homozygous mutant male (bcd/bcd). a. How is it possible for a male homozygous for the mutation to exist? b. Predict the outcome (normal and/or failed embryogenesis) in the F1 and F2 generations resulting from this cross.

Answer 1

(a) The bcd/bcd male must have had a heterozygous mother.
(b) The first generation offspring will all hatch normally, although half of them will be bcd/bcd. In the F2 generation, half the eggs will fail to produce larva. An F1 female who is bcd/bcd will produce no live offspring, but the bcd+/bcd females will produce all live offspring.