多等位基因性状

For the same gene multiple alleles can interact to influence phenotypes like the shape and protein composition of an individual cells.

For example in erythrocytes, or red blood cells the hemoglobin protein has a component encoded by the beta-globin gene for which several different alleles have been identified. Collectively these are the multiple alleles of beta-globin.

For the mutant sickle allele, homozygotes demonstrate stiff, crescent shaped red blood cells that clog vessels, whereas those with the normal allele exhibit flexible disc like erythrocytes that travel easily through the vasculature. Interestingly heterozygotes may display some mildly curved cells, a shape exacerbated under low oxygen.

Since the erythrocyte morphology of heterozygotes falls between that of the homozygotes this is an example of an allele interaction called incomplete dominance. If the sickle allele were dominant heterozygotes would only demonstrate sickle shaped cells which isn't the case.

Molecularly heterozygotes showcase another allele interaction called codominance. This is because the protein products of both the normal allele and sickle allele, which causes hemoglobin proteins to stick together o