Why are alleles IA and IB considered codominant?

1 Answer
Mar 20, 2018

Alleles #IA# and #IB# are considered codominant as both these alleles dominate over recessive allele. #i# .

Explanation:

Alleles #IA# and #IB# produce antigen A and B, respectively. Recessive allele #i# does not produce any antigen . Allele #IA# and allele #IB# present along with recessive allele #i# will dominate over allele #i# and produce antigen A and B, respectively.

However, when both these dominant alleles #IA# and #IB# are present together, none of these is able to interfere with the expression of other allele. Thus, the genoptype #IAIB# will produce both antigens A and B.

The presence of antigen on R.B.C.s determines the blood group of the individual.

There are 4 blood groups: A, B, AB and O. The genotype of differrent blood groups clearly explains the phenomenon of codominance.

Genotypes of 4 blood groups are as follows:

Blood group A: #IAIA, IAi#
Blood group B : #IB IB , IB i#
Blood group AB: #IAIB#
Blood group O: #ii#