Question

With the help of one example, explain the phenomena of co-dominance and multiple allelism in human population.

Answer 1

ABO blood group in human being is an example of multiple allelism.

There alleles for the gene I  i.e. I^A,I^B,i.

When I^A and I^B are present together the blood  group is AB.

Both A and  B. are expressed and is called codominance.

Detailed Answer: 

ABO blood grapes in human population is an example of multiple allelism and codominance. There are three alleles of gene l, i.e., I^A,I^B and i. thus exhibiting multiple alIelism. Out of these three alleles any two alleles may occur in human being, one alleles is contributed from each parent.

The alleles I^A + I^B are dominant over allele i and produce A and B phenotypes respectively. But however when alleles I^A and I^B are present together both of them express equally and independently producing AB phenotype. This is a phenomenon called codominance.