Question

You isolate two new loss-of-function mutations in C. elegans which affect the differentiation of sensory neurons. In one mutation, nos-1, the worms cannot sense where the food is in their environment. In the second, yum-1, they are hypersensitive to their food source. Which of the following regulatory pathways is/are consistent with the results so far? Note that a pointed arrow ( → ) indicate activation and the blunt arrow ( ---| ) indicates inhibition.

Question options:

a) nos-1 ---| yum-1 ---| food perception

b) nos-1 ---| yum-1 → food perception

c) yum-1 ---| nos-1 → food perception

d) yum-1 ---| nos-1 ---| food perception

Answer 1

Both a) and c) are correct.

In a) if nos-1 is mutated, yum-1 is always active and food perception is constantly inhibited. If yum-1 is mutated, food-perception is always active and worms are hypersensitive to food.

In c) if nos-1 is mutated, food perception cannot occur as nos-1 is required for food perception. If yum-1 is mutated, nos-1 is constantly active and food perception is always turned on.