Question

Three Mark Questions :
(a) Explain the phenomena of multiple allelism and codominance taking ABO blood group as an example
(b) What is the phenotype of (i) |Ai (ii) ii.

Answer 1

The inheritance pattern of ABO blood groups in humans shows codominance. The allele i${}^A$ and i${}^B$ are codominant and when both of them are present together both will show equal expression in the phenotype and hence, the resulting blood group will be AB. In ABO blood grouping, three alleles are seen I${}^A$, i${}^A$ and i, that result in the different genotypes as:

i${}^A$ i${}^A$: Blood group A

i${}^A$ i: Blood group A

i${}^B$ i${}^B$: Blood group B

I${}^B$ i: Blood group B

i${}^A$ i${}^B$: Blood group AB

ii: Blood group O

Therefore, ABO blood grouping can be said to be showing multiple allelism, since there are more than one allele.

b)Phenotype of i)${}^A$i will be blood group A and that of ii) ii will be blood group O.