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 number of phenotypes in ABO blood groups is :
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 4
Three alleles give six genotypes but only four phenotypes: A, B, AB and O.
Option (2) 4 — Correct. The three alleles IA, IB and i give six genotypes, but only four phenotypes: blood groups A, B, AB and O. This is because IA and IB are each dominant over i.
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.