Encyclopedia of Animal Cognition and Behavior

Living Edition
| Editors: Jennifer Vonk, Todd Shackelford

Overdominance Hypothesis for Male Homosexuality

  • Andrea S Camperio CianiEmail author
Living reference work entry
DOI: https://doi.org/10.1007/978-3-319-47829-6_1928-1


The complete definition of overdominance according to the Merriam-Webster dictionary is “the condition wherein a heterozygote produces a phenotype more extreme or better adapted than that of the homozygote.” In other words, overdominance produces a balanced polymorphism where the heterozygote has a greater phenotype value and it is more fit than the homozygous state for either of the alleles that it comprises. Hence, overdominance can also be described as heterozygote advantage, wherein heterozygous individuals have a higher fitness than homozygous individuals.

To clarify the effect of overdominance, the example of sickle cell anemia can be considered. Consulting the American Heart, Lung, and Blood Institute guidelines, it appears that this condition is determined by a single polymorphism. Sickle cell anemia results in an abnormality in the oxygen-carrying protein hemoglobin; homozygote carriers develop a specific syndrome with number of health problems. Carrier of these...

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Copyright information

© Springer International Publishing AG 2018

Authors and Affiliations

  1. 1.University of PadovaPadovaItaly

Section editors and affiliations

  • Sarah Dunphy-Lelii
    • 1
  1. 1.Bard CollegeAnnandale-On-HudsonUSA