Codominance

In the phenomenon of co dominance, dominant and recessive alleles lack typical dominant and recessive relationships. In the heterozygous conditions both the alleles of genes are capable of expressing themselves and therefore in the heterozygote, the traits occur side by side. The F2 progeny shows the phenotype and genotypic ratios of 1:2:1.

The best example of co dominance is found in cattle. In one breed of cattle genotype Iw produces white coat colour of the cattle where as Ir genotype expresses red color coat.

What is interesting to note here is that F1 heterozygotes posseses a roan coat colour which is no an intermediate colour between red and white but has a mixture of red hair and white hair. Blood groups A and B are also codominated. Persons with homozygous A & B when marry produce children with AB group. The MN blood group also exhibits codominance. dominance, dominant and recessive alleles lack typical dominant and recessive relationships. In the heterozygous conditions both the alleles of genes are capable of expressing themselves and therefore in the heterozygote, the traits occur side by side. The F2 progeny shows the phenotype and genotypic ratios of 1:2:1.

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