Situation in which the phenotype of the heterozygote is intermediate between those of the two homozyotes.
Incomplete dominance is typically illustrated in terms of flower color, with the homozygous dominant phenotype red, the color of the homozygous recessive white, and the heterozygote pink.
As with codominance, the phenotypic and genotypic ratios coincide with incomplete dominance. That is, given a monohybrid cross, those ratios would be 1:2:1. See by contrast complete dominance.
Physiologically what is going on with incomplete dominance is that insufficient gene product is produced from one allele alone to match the phenotype associated with two alleles. Thus, in the flower color example, insufficient red pigment is produced, resulting in a lighter red, i.e., pink.
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