Fig. 2.

Mechanisms underlying the emergence of new SDGs and sex chromosomes. (a, b) Overview of the general processes of sex chromosome replacement and the establishment of SDGs. (c) Mechanisms underlying new SDG emergence driven by TEs. Left: TE insertions near an preexisting SDG or a sex-related gene triggering translocation or gene duplication through its transposition mechanisms. Top right: TE insertion into an allele of a sex-related gene creates sex differences in gene expression. Bottom right: Gene duplication followed by TE insertion and exonization lead to the emergence of an SDG with a new function.