Question

ABO blood group system is due to

• A. multifactor inheritance
• B. incomplete dominance
• C. multiple allelism
• D. epistasis

Answer 1

The Correct Option is C

The ABO blood group system is one of the most well-known systems for classifying human blood groups. This classification is based on the presence or absence of certain antigens and antibodies in the blood. The ABO blood group system is an example of multiple allelism. Let's understand this in detail:

Explanation:

1. Definition: Multiple allelism refers to the presence of more than two alleles for a gene within a population. An individual can possess only two alleles at a time, one from each parent, but there can be multiple allele types present within a population.
2. ABO Blood Groups: The ABO blood group system is determined by the I gene, which has three types of alleles: I^A, I^B, and I^O (or i).
   • I^A allele produces the antigen A on the surface of red blood cells.
   • I^B allele produces the antigen B.
   • I^O or i allele produces no antigen (making it recessive).
3. Combinations and Blood Types: Depending on the combination of these alleles, different blood types are formed:
   • Type A: Can be I^AI^A or I^Ai
   • Type B: Can be I^BI^B or I^Bi
   • Type AB: I^AI^B (showing co-dominance)
   • Type O: ii
4. Why Not Other Options?
   • Multifactor Inheritance: Refers to traits controlled by multiple genes and environmental factors, not applicable here.
   • Incomplete Dominance: Involves a blending of traits, which ABO does not exhibit.
   • Epistasis: Involves interaction between different genes, not the case in ABO blood groups.

Therefore, the ABO blood group system is due to multiple allelism. The existence of three alleles leads to various combinations, resulting in different blood types.