Figure 1. Sex determination pathways in diverse model organisms.

Variations in an XX/XY GSD system. Differences among species are evident throughout all stages of the sex determination hierarchy, although each of the pathways converge on conserved downstream regulators in the DM domain gene family that are essential for male development. For simplicity and clarity, in each gene network shown a number of peripheral, relatively minor, or sex non-specific regulators have been omitted. Regulatory interactions (solid lines) are meant to indicate the regulatory logic of each pathway but do not necessarily imply direct regulation. Dashed lines indicate temporal relationships.