Heterogametic sex

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G-banding
Drosophila sex determination system. In Drosophila, males are the heterogametic sex.

The heterogametic sex (or digametic sex) is the sex of a species where an individual's

female sex, where each gamete's sex chromosomes are X and X. This arrangement is understood within the XY sex-determination system.[1]

Non-human animals often have different sex arrangements than humans. In birds, the male sex is the homogametic sex, having two Z chromosomes, while the female sex is the heterogametic sex, with one Z and one W chromosome. In

platypuses, the male sex is heterogametic while the female sex is the homogametic sex. Among the insects, Lepidopterans (butterflies and moths) have heterogametic females, but in Drosophila, males are the heterogametic sex. This arrangement is known as the ZW sex-determination system.[2]

Heterogametic sex determination systems typically have an approximately equal sex ratio, with distributions of sexes conforming to binomial variance.[3] However, in practice, some populations deviate from this expectation, in a phenomenon termed sex ratio distortion. Sex ratio distortion has been observed in mice,[4] mosquitos,[5] and other organisms[6] and can be caused by meiotic drive elements.

Heterogamesis can lead to reduced or absent

achiasmy. For example, most lineages of male Drosophila melanogaster flies are achiasmic, lacking recombination on all chromosomes, although females show recombination.[7]

See also

References

  1. ^ King R.C.; Stansfield W.D.; Mulligan P.K. (2006). A Dictionary of Genetics (7th ed.). Oxford. p. 204.
  2. ISBN 978-0-299-16604-5
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  3. ISBN 9780128132524
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  4. PMID 34740238
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  5. S2CID 84366854
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  6. PMID 36339946
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  7. PMID 12618416
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