Class NEET 2026 ALL Q #2040
COMPETENCY BASED
APPLY
4 Marks 2026 NTA-RE-NEET-2026 MCQ SINGLE
Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R.
Assertion A: In an experiment, Mendel observed that the F1 progeny plants are all tall and none are dwarf.
Reason R: Stem height is a contrasting trait, with tall being dominant and dwarf being recessive.
In the light of the above statements, choose the most appropriate answer from the options given below :
(A) A is not correct but R is correct
(B) Both A and R are correct and R is the correct explanation of A
(C) Both A and R are correct but R is not the correct explanation of A
(D) A is correct but R is not correct
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Correct Answer: B

AI Tutor Explanation

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Detailed Solution

Step 1: Analyze Assertion A

Mendel's monohybrid cross experiment involved crossing pure-breeding tall plants (TT) with pure-breeding dwarf plants (tt). The resulting F1 generation consists entirely of heterozygous (Tt) plants, which phenotypically express the dominant trait, making them all tall. Thus, Assertion A is correct.

Step 2: Analyze Reason R

In Mendelian genetics, stem height is indeed a contrasting trait where the allele for tallness (T) is dominant over the allele for dwarfness (t). This dominance relationship explains why the F1 generation expresses only the tall phenotype. Thus, Reason R is correct.

Step 3: Determine the Relationship

The reason why all F1 progeny are tall (Assertion A) is directly due to the fact that tallness is dominant over dwarfness (Reason R). Therefore, Reason R provides the correct scientific explanation for the observation stated in Assertion A.

Final Answer: B

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Pedagogical Audit
Bloom's Analysis: This is an APPLY question because it requires the student to connect the theoretical principle of dominance to a specific experimental outcome observed by Mendel.
Knowledge Dimension: CONCEPTUAL
Justification: The question tests the understanding of the Law of Dominance and its application to monohybrid cross results.
Syllabus Audit: In the context of NEET, this is classified as COMPETENCY. This question format is standard for the NEET Biology section, assessing the ability to evaluate logical relationships between biological observations and genetic principles.

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