Sex in the wormcounting and compensating X-chromosome dose

Trends Genet. 2000 Jun;16(6):247-53. doi: 10.1016/s0168-9525(00)02004-7.


The nematode Caenorhabditis elegans counts its X chromosomes to determine sex and to activate the process of dosage compensation, which ensures that males (XO) and hermaphrodites (XX) express equal levels of most X-chromosome products. The number of X chromosomes is communicated by a set of X-linked genes called X-signal elements, which repress the master sex-determination switch gene xol-1 via two distinct, dose-dependent molecular mechanisms in XX embryos. X-chromosome gene dosage is compensated by a specialized protein complex that includes evolutionarily conserved components of mitotic and meiotic machinery. This complex assembles on both X chromosomes of hermaphrodites to repress transcription by half. The recruitment of chromosome segregation proteins to the new task of regulating X-chromosome-wide gene expression points to the evolutionary origin of nematode dosage compensation.

Publication types

  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Animals
  • Caenorhabditis elegans / physiology*
  • Dosage Compensation, Genetic*
  • Female
  • Gene Expression Regulation
  • Male
  • Sex
  • Sex Determination Processes
  • X Chromosome*