Practice question

Vulval precursor cells P3.p-P8.p form competence group in central ventral epidermis. During mid-L3, anchor cell positioned over P6.p secretes LIN-3 EGF, activating LET-23 EGFR Ras-MAPK cascade highest in P6.p. This high signal induces primary vulval fate defined by lineage generating central invagination forming vulval tube and connection to uterus. P6.p daughters divide three times producing cells vulE and vulF that attach to anchor cell and utse. In wild type, P6.p invariably generates central vulval lineage, while neighbors become secondary and outer cells fuse to hypodermis, ensuring single vulva positioned correctly.