NEET 2026 ALL Q #2043
COMPETENCY BASED
APPLY
4 Marks 2026 NTA-RE-NEET-2026 MCQ SINGLE
For a person with blood group 'O', which of the following is not a possible combination of parents' blood group genotypes?
(A) Father: $I^{A}I^{A}$ and Mother: $I^{A}i$
(B) Father: $I^{A}i$ and Mother: $I^{B}i$
(C) Father: $I^{A}i$ and Mother: $I^{A}i$
(D) Father: $I^{B}i$ and Mother: $I^{B}i$
Correct Answer: A

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Detailed Solution

Step 1: Understanding the Genetics of Blood Group O

A person with blood group O must have the genotype ii. This means they must inherit one i allele from the father and one i allele from the mother.

Step 2: Analyzing Option (A)

Father: IAIA and Mother: IAi. The father can only pass the IA allele to the offspring. Since the offspring cannot receive an i allele from the father, it is impossible for them to have the ii genotype (Blood group O).

Step 3: Analyzing Options (B), (C), and (D)

In option (B), both parents carry the i allele, allowing for an ii offspring. In option (C), both parents carry i, allowing for ii. In option (D), both parents carry i, allowing for ii. Therefore, these combinations can produce a child with blood group O.

Final Answer: A

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because it requires the student to use the principles of Mendelian inheritance and codominance to predict phenotypic outcomes from specific genotypes.
Knowledge Dimension: CONCEPTUAL
Justification: The student must understand the relationship between alleles (IA, IB, i) and how they interact to determine blood group phenotypes.
Syllabus Audit: In the context of NEET, this is classified as COMPETENCY. This question tests the ability to apply genetic laws to solve problems, which is a core requirement for the NEET Biology syllabus under the 'Genetics and Evolution' unit.

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