ABO blood groups in human beings are controlled by the gene I. The gene I has three alleles - I^A,I^B and i . Since there are three different alleles, six diffrent genotypes are possible. How many phenotypes can occur?

4

The correct answer is Option (4) –4

The ABO blood group system in humans is governed by a pair of genes, consisting of three types of alleles: I^A, I^B, and I^o.

• Alleles I^A and I^B are both dominant, while I^o is recessive.
• Genotypes I^AI^A or I^AI^o result in the A blood group phenotype.
• Genotypes I^BI^B or I^BI^o lead to the B blood group phenotype.
• Genotype I^AI^B leads to the AB blood group phenotype.
• Genotype I^oI^o results in the O blood group phenotype.

In summary, based on the combinations of these alleles, there are four possible blood group phenotypes: A, B, AB, and O. The gene operates with co-dominance and dominance-recessiveness interactions among its alleles to determine the ABO blood group phenotypes.