Dosage compensation

A mechanism for regulating chromosome-wide gene expression based on the ratio of autosomes to sex chromosomes. In C. elegans, the hermaphrodite is XX with two X chromosomes while the male is X0 with only one X chromosome. Dosage compensation machinery in these nematodes reduces expression of genes on both X chromosomes in the hermaphrodite.

Gene silencing

Inactivation of gene expression can occur at both the level of transcription and post-transcription. All silencing mechanisms are identical in that they require a small RNA species to provide the necessary gene sequence specificity and effector molecules that bind to the RNAs to process the RNA and to direct its inhibitory activity. Studies of these mechanisms in C. elegans has elucidated a number of different RNA-mediated post-transcriptional mechanisms. These mechanisms differ in the species of small RNAs involved. The different classes of small RNAs in C. elegans includes, microRNAs (miRNA), small interfering RNAs (siRNAs or rasi's), X-chromosome cluster RNAs (X-cluster), tiny noncoding RNAs (tncRNAs), and Piwi-associated RNAs (piRNAs). Gene silencing is accepted as a defense mechanism that evolved to protect the host from exogenous (foreign) sequence such as viral and transposon sequence. It has also been shown that gene silencing plays a critical role in endogenous gene expression to control the developmental timing of genes require for cell specificity, as well as playing a role in aging.