Bicoid is a maternal effect gene that is essential for the development of head structures in Drosophila. The F₁ generation from a cross of two phenotypically normal flies produces normal embryos, but in the F₂ cross, 25% of the embryos lack heads and die. What was the genotype of the mother in the P generation?

Question

Quizplus · Accepted Answer

The mother in the P generation must have been heterozygous (Bb) because the F1 generation was normal, indicating that the mother provided at least one functional Bicoid allele. In the F2 generation, 25% of the embryos lack heads, suggesting that these embryos are homozygous recessive (bb), which can only occur if the F1 parents were both Bb.

Bicoid Is a Maternal Effect Gene That Is Essential for the Development