In Drosophila melanogaster, the expression of genes Ultrabithorax and Antennapedia can normally be observed in the third thoracic segment which bears a pair of legs as well as a pair of halteres. Homeotic mutations associated with these two genes can give rise to remarkable disturbances in the organization of the adult fly: two pairs of wings in the case of Ultrabithorax, and legs in the place of antennae in the case of Antennapedia. Would you expect these to be gain-of-function or loss-of-function mutations?
A) Loss-of-function for both genes
B) Loss-of-function for Ultrabithorax and gain-of-function for Antennapedia
C) Gain-of-function for Ultrabithorax and loss-of-function for Antennapedia
D) Gain-of-function for both genes

Question

Quizplus · Accepted Answer

Loss of Ultrabithorax transforms the segment into a more anterior identity and gives rise to a pair of wings in this segment. Gain of Antennapedia transforms a head segment such that it bears a leg in the place of an antenna.

In Drosophila Melanogaster, the Expression of Genes Ultrabithorax and Antennapedia