Drosophila mutations such as bcd, if homozygous in the mother, produce offspring with lethal defects, no matter what the genotype of the offspring. For some other genes, the mutant phenotype can be "rescued" by introducing a wild-type allele. What is the reason for these different outcomes?
A)Non-rescuable mutations are of paternal origin.
B)Rescuable mutations act as dominants.
C)bcd is a maternal effect mutation.
D)Rescue requires recombination between the maternal and introduced alleles.
E)bcd is a Hox gene.

Question

Quizplus · Accepted Answer

bcd is a maternal effect mutation, meaning the phenotype of the offspring is determined by the genotype of the mother. If the mother is homozygous mutant for bcd, then the offspring will have lethal defects regardless of their own genotype. This is because the mother's mutant bcd gene affects the substance called bicoid mRNA that is deposited in the egg during oogenesis and is required during early embryonic development.

Drosophila Mutations Such as Bcd, If Homozygous in the Mother