Read the given passage and answer the question.

ABO blood groups in human beings are controlled by the gene $I$. The plasma membrane of the red blood cells has sugar polymers that protrude from its surface and the kind of sugar is controlled by the gene. The gene ($I$) has three alleles $I^A, I^B$ and $i$. The alleles $I^A$ and $I^B$ produce a slightly different form of the sugar while allele $i$ does not produce any sugar. Because humans are diploid organisms, each person possesses any two of the three $I$ gene alleles. $I^A$ and $I^B$ are completely dominant over $i$.

Select the correct option for number of alleles present in ABO blood groups:

Three different alleles

The correct answer is Option (2) → Three different alleles

ABO blood groups are controlled by the gene I. The gene (I) has three alleles I ^A , I ^B and I. In this system, individuals can possess red blood cells categorized as type A (I^A), type B (I^B), or type O (i), representing three different alleles. These alleles can combine in various ways according to Mendel's Laws of Inheritance, resulting in genotypes that give rise to type A, type B, type AB, or type O blood. Type A blood arises from either two A alleles (I^AI^A) or a combination of one A allele and one O allele (I^Ai). Similarly, type B blood is determined by either two B alleles (I^BI^B) or one B allele and one O allele (I^Bi). Type O blood, on the other hand, is exclusively associated with two recessive O alleles (ii). These examples demonstrate instances of simple or complete dominance in the context of multiple allelism.