Practice question

LIN-3 is epidermal growth factor family ligand synthesized in anchor cell under control of EGL-38 Pax2 and lag-2 gonadal inputs. The gene encodes transmembrane protein cleaved by rhomboid protease SUP-17 and ADAM10 metalloprotease, releasing EGF domain that diffuses short distance as morphogen. Binding receptor LET-23 on underlying vulval precursors activates tyrosine kinase signaling, Ras activation, MAPK phosphorylation. Dosage matters critically: low expression fails to induce, high dose causes multivulva phenotype beyond P6.p. Thus LIN-3 functions as primary inductive cue coordinating uterine-hypodermal development.