Genetic mechanisms of sex determination are unexpectedly diverse and change rapidly during evolution. We review the role of genetic conflict as the driving force behind this diversity and turnover. Genetic conflict occurs when different components of a genetic system are subject to selection in opposite directions. Conflict may occur between genomes (including paternal-maternal and parentalzygo...

Five newly identified sex-biased transcripts in Drosophila are full of surprises: although they are found in fly heads, and manipulating two of them affects mating behaviors, their genes are expressed sex-specifically in non-neural tissues. The way these genes are regulated suggests new complexities in the sex determination pathway.

We present a model to show that, when sex depends on environment rather than genotype, the sex expressed under relatively unfavorable conditions will be more abundant. This result refers to numbers of males and females in the population. By contrast, no clear prediction can be made about the allocation of resources to the two sexes. The model is constructed to highlight the logical relationship...