Question

You find a mutant Drosophila larva that is lacking anterior structures. You know that this embryo had normal amounts of Bicoid protein. What other type of mutation could cause this result?

A. A hunchback mutation that inhibits Hunchback production.
B. A hunchback mutation that causes Hunchback overproduction.
C. A maternal effect gene mutation that inhibits the production of a maternal gene product.
D. A segmentation gene mutation that inhibits production of a segmentation gene product.
E. A segmentation gene mutation that causes the overproduction of a segmentation gene product.

Answer 1

A mutation in the Hunchback gene that inhibits Hunchback production would likely cause a Drosophila larva to lack anterior structures, as Hunchback is activated by normal levels of Bicoid protein to repress posterior-defining genes.

Step-by-step explanation:

Considering that the Drosophila larva in question has normal amounts of Bicoid protein, which is an anterior morphogen, we can eliminate mutations related to maternal effect genes that affect this protein specifically. Bicoid protein normally activates transcription of the Hunchback gene, so a mutation that affects Hunchback production could prevent it from repressing genes that define posterior structures. This may lead to the absence of anterior structures even in presence of normal Bicoid levels. Therefore, the type of mutation that could cause a Drosophila larva to lack anterior structures despite normal Bicoid protein levels would likely be option A: A hunchback mutation that inhibits Hunchback production.