Question

You are working in a Drosophila lab, and find a larva with two anterior ends. Both a normal larva and the mutant larva are shown below. What is the most likely explanation for the mutant larva phenotype?

A. there is a mutation in the bicoid gene causing no functional Bicoid protein to be made
B. the nurse cells that produce the Bicoid protein are defective, so there is no protein at either end of the embryo
C. there is a mutation in a homeotic gene
D. there is a high concentration of the Bicoid protein at both ends of the mutant embryo
E. a protein encoded by a segment polarity gene is not degraded correctly and accumulates in both ends of the embryo

Answer 1

The most likely explanation for a Drosophila larva with two anterior ends is a mutation in a homeotic gene, such as a Hox gene, which is essential in determining the body segment identity during development.

Step-by-step explanation:

The phenotype of a larva with two anterior ends is most likely due to the mutation in the Hox gene. These genes are crucial for establishing the anterior-posterior axis during embryonic development in Drosophila melanogaster. A mutation such as in the Antennapedia gene, which is a Hox gene, is known to cause dramatic changes in body segment identity, an example being legs growing from the head in place of antennae. Therefore, the most likely explanation for the mutant larva having two anterior ends is option C, 'there is a mutation in a homeotic gene'.