Overdominance is a condition in genetics where the phenotype of the heterozygote lies outside of the phenotypical range of both homozygote parents.
 The Gillespie Model
Population Geneticist John H. Gillespie established the following model :
Where h is the heterozygote effect and s is the recessive allele effect. Thus given a value for s (ie: 0<s<1), h can yield the following information:
 Overdominance in human genetics
In humans, sickle cell anemia is a condition that is determined by a single polymorphism. Possessors of this slightly deleterious allele have lower life expectancy, with homozygotes rarely reaching 50 years of age. However, this allele also yields some resistance to malaria. Thus in regions where malaria exerts or has exerted a strong selective pressure, sickle cell anemia has been selected for its conferred partial resistance to the disease. While homozygotes will have either no protection form malaria or a dramatic propensity to sickle cell anemia, heterozygotes enjoy a partial resistance to both.
In the Gillespie Model, this means an h<0
 See also
This article is based on one or more articles in Wikipedia, with modifications and additional content by SOURCES editors. This article is covered by a Creative Commons Attribution-Sharealike 3.0 License (CC-BY-SA) and the GNU Free Documentation License (GFDL). The remainder of the content of this website, except where otherwise indicated, is copyright SOURCES and may not be reproduced without written permission. (For information use the Contact form.)
SOURCES.COM is an online portal and directory for journalists, news media, researchers and anyone seeking experts, spokespersons, and reliable information resources. Use SOURCES.COM to find experts, media contacts, news releases, background information, scientists, officials, speakers, newsmakers, spokespeople, talk show guests, story ideas, research studies, databases, universities, associations and NGOs, businesses, government spokespeople. Indexing and search applications by Ulli Diemer and Chris DeFreitas.
For information about being included in SOURCES as a expert or spokesperson see the FAQ or use the online membership form. Check here for information about becoming an affiliate. For partnerships, content and applications, and domain name opportunities contact us.