This document discusses sex determination in the plant species papaya. It describes how papaya can have three sex forms - male, female, and hermaphrodite. The genetics of papaya sex determination have been studied and several hypotheses have been proposed, including it being controlled by a single gene with three alleles or a group of linked genes on the sex chromosome. Current research indicates sex is determined by a pair of primitive sex chromosomes, with two slightly different Y chromosomes controlling male vs hermaphrodite sex. Molecular genetics techniques are helping researchers further understand the genes and pathways involved in papaya sex determination.