Question

Identify the wrong statement with reference to the gene T that controls ABO blood groups.

• A. The gene (I )has three alleles.
• B. A person will have only two of the three alleles.
• C. When $I^A$ and $I^B$ are present together, they express same type of sugar.
• D. Allele 'i' does not produce any sugar,

Answer 1

The Correct Option is C

The question tests your understanding of the genetic basis behind the ABO blood group system. Let’s explore the basic genetics of ABO blood groups to understand why the identified statement is incorrect.

1. The ABO blood group system is controlled by the gene \(I\) which has three alleles: \(I^A\), \(I^B\), and \(i\).
2. Each individual inherits two alleles for this gene, one from each parent. Therefore, a person will have any two of these alleles, making this fact true.
3. The alleles \(I^A\) and \(I^B\) are codominant. This means that when both \(I^A\) and \(I^B\) are present together, they express their respective antigens (type A sugar and type B sugar) on the surface of red blood cells. Therefore, the statement suggesting that they express the same type of sugar is incorrect since they express different sugars.
4. The allele \(i\) is recessive and does not add any sugar, thus resulting in the expression of the O blood group when two \(i\) alleles are inherited.

Thus, the incorrect statement is: "When \(I^A\) and \(I^B\) are present together, they express the same type of sugar." Instead, they express different sugars corresponding to types A and B antigens.