The phenomenon in which both alleles in a heterozygote are expressed in the phenotype. Thus in certain plants that possess a series of alleles governing incompatibility (see S alleles), an individual plant that has two different alleles both relatively high in the dominance series may be incompatible with any plant possessing either of these dominant alleles (i.e. both alleles are exhibited by the phenotype). In other cases the one allele may be completely dominant to the other and such a plant would be able to cross with another plant possessing the same recessive allele. This illustrates that codominance relationships do not necessarily exist for all the alleles of a gene. Compare incomplete dominance. |
