Question

Genetics of blood groups in human illustrates

• A. Multiple allelism and codominance
• B. Multiple allelism and pseudodominance
• C. Pseudoallelism and codominance
• D. Incomplete dominance and multiple allelism

Answer 1

Answer: (A)

Multiple allelism and codominance

There are four blood groups in humans, A, B, AB and O which are controlled by a set of three multiple alleles present on chromosome number 9. The genes controlling blood types have been labeled as i (stands for isohaemoagglutinin). The six genotypes that give rise to four phenotypes represent various combinations of three ABO alleles i.e. I${}^A$, I${}^B$ and i.

Both I${}^A$ and I${}^B$ are dominant to i. The ABO blood series give a good example of codominance. Heterozygous I${}^A$/I${}^B$ individuals are blood group AB.

Hence, human blood grouping illustrates both multiple allelism and codominance. So, the correct answer is 'Multiple allelism and codominance'.