Heterogametic sex

Heterogametic sex (digametic sex) refers to the sex of a species in which the sex chromosomes are not the same. For example, in humans, males, with an X and a Y sex chromosome, would be referred to as the heterogametic sex, and females having two X sex chromosomes would be referred to as the homogametic sex.[1]

However, in birds, and some reptiles, males have two Z sex chromosomes and so are the homogametic sex, while females, with one Z and one W chromosome, are the heterogametic sex. Platypus males are heterogametic while females are homogametic. Among the insects, Lepidopterans (butterflies and moths) have heterogametic females, but in Drosophila, males are the heterogametic sex.[2]

Heterogamesis can lead to reduced or absent meiotic recombination between the sex chromosomes, and in some species this extends to the autosomes, a phenomenon called achiasmy. For example, most lineages of male Drosophila melanogaster flies are achiasmic, lacking recombination on all chromosomes, although females show recombination.[3]

See also


  1. King R.C.; Stansfield W.D.; Mulligan P.K. (2006). A Dictionary of Genetics (7th ed.). Oxford. p. 204.
  2. James Franklin Crow; William F. Dove, eds. (2000). Perspectives on genetics: anecdotal, historical, and critical commentaries, 1987–1998. Madison, WI: University of Wisconsin Press. ISBN 978-0-299-16604-5.
  3. Lenormand, Thomas (February 2003). "The Evolution of Sex Dimorphism in Recombination". Genetics. 163 (2): 811–22. PMC 1462442. PMID 12618416.

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