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 \(i\).
The genotype of Universal donor is:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → \(ii\)
The universal donor has blood group O. The allele i makes no sugar, so the red blood cells carry neither A nor B sugar, and the genotype is ii.
Option (1) \(I^A\, i\) — Incorrect. IA is dominant over i, so only IA expresses and the red blood cells carry the A sugar. This is blood group A, not O.
Option (2) \(I^B\) — Incorrect. IB alone is not a diploid genotype; IBIB or IBi gives group B.
Option (3) \(ii\) — Correct. A universal donor has blood group O, whose red cells carry neither the A nor the B sugar. Group O comes only from two recessive alleles, so the genotype is ii.
Option (4) \(I^AI^B\) — Incorrect. IAIB gives group AB, the universal recipient.
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.