from The American Heritage® Dictionary of the English Language, 4th Edition
- n. An organism that has different alleles at a particular gene locus on homologous chromosomes.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. A diploid individual that has different alleles at one or more genetic loci.
- n. A bacteriophage that has two different copies of its genetic material and so produces two types of offspring.
from The Century Dictionary and Cyclopedia
- n. A zygote formed by the union of two unlike gametes.
- n. In Mendelian phraseology, a hybrid animal or plant which combines the characters of two dissimilar parents; a mule-form.
- Of or pertaining to a fertilized egg, or to origin from a fertilized egg, which is formed by the union of two opposite allelomorphic germ-cells: as, heterozygote characters.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. (genetics) an organism having two different alleles of a particular gene and so giving rise to varying offspring
Other common autosomal recessive diseases such as sickle cell anemia have been found to protect carriers from other diseases, a concept known as heterozygote advantage.
I added it to the list on our Instructors' Blog, stated as follows:Students should be able to define dominance as a particular relationship between the effects of two alleles; dominance is said to exist when the phenotype of the heterozygote is the same as that of a homozygote for one of the alleles the 'dominant' one.
This is where the heterozygote has a higher fitness than either homozygote.
He constructed a model with populations subdivided into numerous, semi-isolated subpopulations, or demes, in which spontaneous chromosome rearrangements with heterozygote disadvantage occur.
Lande 1979 looked at the problem of fixation for chromosomal rearrangements with heterozygote disadvantage.
But if two dominant, or two recessive, alleles occur together in a heterozygote, interesting things can happen.
The example is of heterozygote superiority, though any example where the allelic effects on phenotype are non-additive would do.
A final, important point is that even with just those two simple mutations the process is convoluted almost to the point of incoherence.17 Even with just the sickle and C genes—with heterozygote versus homozygote advantage and with varying detrimental effects—the interplay of the mutant and normal genes is chaotic and tangled.
So, the idea is that some allele exists which confers an evolutionary benefit when present in the heterozygote stronger sperm, for example, and confers homosexuality in the homozygote.
A1A2 heterozygote produces gametes bearing the A1 and A2 alleles in equal proportion.