A powerful approach to identifying genes of a developmental pathway is to screen for mutations that suppress or enhance the phenotype of interest. This approach was undertaken to elucidate the genetic pathway controlling C. elegans vulval development. .

Part A

A lin-3 loss-of-function mutant with a vulva-less phenotype was mutagenized. Based on your knowledge of the genetic pathway, what types of mutations will suppress the vulva-less phenotype?

Check all that apply.

A. gain-of-function intracellular signal molecule (LET-60) activated by lin-3 mutants
B. loss-of-function intracellular signal molecule (LET-60) activated by lin-3 mutants
C. loss-of-function lin-3 receptor mutants
D. loss-of-function lin-3 mutants
E. gain-of-function lin-3 receptor mutants

Part B

In a complementary experiment, a gain-of-function let-23 mutant with a multi-vulva phenotype was also mutagenized. What types of mutations will suppress the multi-vulva phenotype?

Check all that apply.

A. gain-of-function intracellular signal molecule (LET-60) activated by lin-3 mutants
B. gain-of-function lin-3 receptor mutants
C. loss-of-function lin-3 receptor mutants
D. loss-of-function intracellular signal molecule (LET-60) activated by lin-3 mutants

Genetic suppressors are widely used in molecular genetics to study gene function in specific developmental stages and target tissues. Suppressing mutations are second mutations triggered at a different site from the mutation of interest in order to suppress the phenotypic effects caused by the first mutation. Caenorhabditis elegans is a model organism to produce genetic suppressors by taking advantage of its rapid generation time and large populations, which enables the application of rapid and powerful mutation screening procedures in the same experiment. In addition, this species reproduces by self-fertilization, thereby both dominant and recessive suppressors can be easily obtained.