CBSE 2025 · Region 2 · Set 2 · Q13 · 1 mark
Assertion (A) : 'XX - XY' type of sex-determination mechanism is an example of male heterogamety.
Reason (R) : In birds male heterogamety is observed as males produce two different types of gametes.
Official answer
From CBSE’s own marking scheme for this paper.
(C)
(A) is true, but (R) is false.
Principles of Inheritance and VariationSex DeterminationUnderstandassertion_reasonmedium
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CBSE Class 12 Biology past-paper question from the 2025board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.