Recessive mutations in the sxl gene in Drosophila are lethal in XX females because
A) sxl functions as a repressor of male-specific dosage-compensation genes.
B) recessive mutations indicate an increase in sxl activity.
C) these mutations are the result of a loss of both X chromosomes.
D) sxl is required for transcription of male-specific genes.
E) recessive mutations are always lethal.

Question

Quizplus · Accepted Answer

The sxl gene is responsible for the regulation of sex determination in Drosophila. In XX females, sxl acts as a repressor of male-specific dosage-compensation genes. Recessive mutations in the sxl gene would result in decreased or non-functional sxl protein, leading to an inability to repress male-specific genes in XX females. This would result in a lethal phenotype as the female cannot properly develop.

Recessive Mutations in the Sxl Gene in Drosophila Are Lethal