The C. elegans hermaphrodite can be considered as a female that makes sperm for a short period. This pathway allows the required transient switch of the hermaphrodite germ line during the L4 stage to the male mode and then back again to the female mode. However, HER-1 shows no significant similarity to Hedgehog. TRA-2, although similar in size and conformation to Patched, also shows no significant amino acid sequence similarity, and the remaining components so far do not appear homologous. Therefore, the her-1 and hedgehog pathways are only distantly related if at all, and the former so far appears to be novel, not yet encountered in other systems.
Dosage compensation equalizes X chromosome expression in the two sexes.
In C. elegans the genes for dosage compensation control X expression by globally regulating transcript levels of X-linked genes, implying a common regulatory element for most of the genes on the X chromosome. The genes controlling dosage compensation have been identified by mutations that effect X chromosome expression and were identified as sex-specific lethals. The SDC gene products are part of a complex in XX animals that binds to the X chromosome at many sites, apparently changing the chromatin configuration to globally turn down X-linked gene expression by a factor of two. If sex is chromosomally determined, some mechanism of dosage compensation is required to equalize sex chromosome expression in the two sexes. The sex determining genes interact in a complex regulatory pathway, which was proposed on the basis of genetic analysis and has been largely confirmed by molecular analysis.