Practice question

Loss-of-function lin-3 eliminates anchor cell inductive cue essential for vulvogenesis. In wild type, anchor cell expresses lin-3 at early L3 stage, activating LET-23/MAPK cascade in VPCs through SEM-5, LET-60, LIN-45, MEK-2, MPK-1 phosphorylation of transcription factors. Mutants lacking LIN-3 fail to trigger Ras signaling, so P5.p-P7.p never adopt vulval fates and fuse with hypodermis via EFF-1, remaining epidermal. Result is vulvaless animals unable to lay eggs, exhibiting bag-of-worms phenotype where larvae hatch inside mother. Rescue by heat-shock lin-3 restores induction confirming indispensable inductive role.