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 into the embryo. What is the reason for these different outcomes?
A) Non- rescuable mutations are of paternal origin.
B) bcd is a Hox gene.
C) Rescuable mutations act as dominants.
D) Rescue requires recombination between the maternal and introduced alleles.
E) bcd is a maternal effect mutation.

Question

Quizplus · Accepted Answer

The different outcomes are due to the nature of the mutations. bcd (bicoid) is a maternal effect mutation, meaning the phenotype of the offspring is determined by the genotype of the mother, not the genotype of the offspring itself. This is why introducing a wild-type allele into the embryo can't rescue the phenotype for maternal effect mutations like bcd, but can for other types of mutations where the offspring's genotype directly influences the phenotype.

Drosophila Mutations Such as Bcd, If Homozygous in the Mother