CBSE 2026 · Region 4 · Set 1 · Q14 · 1 mark
Assertion (A) : The human blood group 'AB' exemplifies co-dominance. Reason $\displaystyle (R)$ : The gene for human blood group trait exists in three allelic forms $\displaystyle \mathrm{I}^{\mathrm{A}}, \mathrm{I}^{\mathrm{B}}$ and i.
Official answer
From CBSE’s own marking scheme for this paper.
(B)
Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
Principles of Inheritance and VariationInheritance of One GeneUnderstandassertion_reasoneasy
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CBSE Class 12 Biology past-paper question from the 2026board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.