Practice question

Anchor cell LIN-3 forms graded spatial distribution across P3.p-P8.p equivalence group functioning as classic morphogen. High concentration at P6.p activates strong EGFR MAPK output surpassing threshold for primary 1° fate via egl-17 FGF and lin-39 targets inducing vulE vulF toroids. Lower concentration plus lateral LIN-12 Notch activation induced by DSL ligands APX-1, LAG-2 from P6.p induces secondary 2° fate in P5.p and P7.p expressing lip-1 phosphatase and lst repressors. Absence leads to tertiary 3° hypodermal fate. Dosage experiments displacing anchor cell demonstrate dose-dependent switching.