The platyfish has W, X, and Y sex chromosomes. Females are WY, WX, or XX and males are YY and XY. It is possible to generate WW fish in the lab, but in the environment they are presumably embryonic lethal. It is presently not known how sex is determined in these fish, but there are some theories consistent with how sex is determined in other systems. Propose a repression based mechanism to explain sex determination in these fish.
My initial thoughts would be that W and X produces repressor proteins and that Y produces a protein which acts an an effector; this would lead to the result that lack of transcription results in the female condition and transcription results in the male condition. However, this theory doesn't account for the lack of WW genotype in the population. Any thoughts?