Two types of sex determination in a nematode

Nature. 1983 Jul 21-27;304(5923):267-8. doi: 10.1038/304267a0.


Sex in the nematode Caenorhabditis elegans is normally determined by a genic balance mechanism, the ratio of X chromosomes to autosomes, so that XX animals are self-fertilizing hermaphrodites and X0 animals are males. However, recessive mutations of the autosomal gene tra-1 III cause both XX and X0 animals to develop into males, and a linked dominant mutation causes both XX and X0 animals to develop into females. Here I show that these two kinds of mutation are allelic, and that stable mutant strains can be constructed in which sex is determined not by X-chromosome dosage but by the presence or absence of a single active gene. In these strains the autosomes carrying the tra-1 locus are in effect homomorphic Z and W sex chromosomes, and the sexes are homogametic ZZ males and heterogametic ZW females, in contrast to the wild-type arrangement of homogametic XX hermaphrodites and heterogametic X0 males.

MeSH terms

  • Alleles
  • Animals
  • Caenorhabditis / genetics*
  • Female
  • Genes, Dominant
  • Genetic Complementation Test
  • Male
  • Mutation
  • Sex Chromosomes / physiology
  • Sex Determination Analysis*