Question

In incomplete dominance and co-dominance, genotypic and phenotypic ratios are identical. Explain how codominance differs from incomplete dominance in phenotypic nature of their hybrids?

Answer 1

In both incomplete dominance and codominance, both phenotypic and genotypic ratios are identical 1:2:1 in F${}_2$ generation. In incomplete dominance, the phenotype of hybrid is intermediate between the two parents as both the alleles express themselves partially. However, in codominance, there is no intermediate expression as both the alleles express themselves equally. In incomplete dominance, the phenotypic effect of one allele is more prominent than the other while in codominance the phenotypic effect of both the alleles is equally prominent and therefore, they produce altogether a third type of phenotype.