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. 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?

Verified step by step guidance

1. Understand the genetic pathway: The vulval development in C. elegans is controlled by a signaling pathway involving the LIN-3 protein, which acts as a ligand for the EGFR (epidermal growth factor receptor) pathway. A loss-of-function mutation in lin-3 disrupts this signaling, leading to a vulva-less phenotype.
2. Identify suppressor mutations: Suppressor mutations are those that restore the phenotype despite the original mutation. In this case, mutations that enhance downstream signaling in the pathway or bypass the need for LIN-3 could suppress the vulva-less phenotype.
3. Consider downstream components: Mutations in genes encoding downstream components of the EGFR pathway, such as gain-of-function mutations in the receptor (let-23) or downstream signaling molecules (e.g., ras-1 or mpk-1), could enhance signaling and suppress the vulva-less phenotype.
4. Evaluate negative regulators: Loss-of-function mutations in negative regulators of the pathway, such as gap-1 (a GTPase-activating protein) or lin-15 (a repressor of vulval development), could also suppress the vulva-less phenotype by increasing pathway activity.
5. Design experimental approach: To identify suppressor mutations, mutagenize the lin-3 loss-of-function mutant and screen for individuals that develop a vulva. Analyze the genetic changes in these suppressor mutants to determine which genes are involved in restoring the phenotype.

Key Concepts

Gene Function and Mutations

Gene function refers to the specific role a gene plays in the development and functioning of an organism. Mutations can alter gene function, leading to phenotypic changes. In the context of the question, a loss-of-function mutation in the lin-3 gene results in a vulva-less phenotype, indicating that lin-3 is essential for vulval development. Understanding how different mutations can suppress or enhance this phenotype is crucial for identifying genetic interactions.

Suppressor Mutations

Suppressor mutations are genetic changes that counteract the effects of a primary mutation, restoring the normal phenotype. In this case, mutations that would suppress the vulva-less phenotype could either enhance the function of downstream genes in the pathway or compensate for the loss of lin-3 function. Identifying these suppressor mutations helps elucidate the genetic interactions and pathways involved in vulval development.

Genetic Pathways

Genetic pathways are networks of genes that interact to control specific biological processes. In C. elegans vulval development, various genes work together in a pathway influenced by lin-3. Understanding the components and interactions within this pathway is essential for predicting how mutations can affect the phenotype, particularly in identifying which mutations might suppress the effects of a lin-3 loss-of-function mutation.