Question

The ABO system is an example of what kind of inheritance? __________________ alleles

Answer 1

Ans. ABO blood group in humans is controlled by three alleles I⁰, I^A and I^B. The allelic pair is located on chromosome 9 and may occur in possible combinations I⁰I^A, I⁰I^B, I^AI^A, I^BI^B, I^AI^B, or I⁰I⁰. Allele I⁰ is recessive to both I^A and I^B.

# When present along with I^A (genotype I⁰I^A) or I^B (genotype I⁰I^B), the allele I⁰ is not expressed indicating that alleles I^A and I^B show complete dominance over it.

# When both alleles I^A and I^B are simultaneously inherited, both the antigen A and B are simultaneously expressed on RBC cell surface. So, alleles I^A and I^B exhibit co-dominance.

# The ABO system is an example of complete dominance inheritance (I^A and I^B is dominant over I^O) as well as Co-dominance inheritance (alleles I^A and I^B are co-dominant to each other).