alleryIn DNA, the base pairing A-T and G-C reflects that
AA and G have the same molecular weight
BT and C pair freely as both are pyrimidines
CATP cannot be in DNA
DA-T = 2 H-bonds, G-C = 3, fits the helix
Answer & Solution
Correct answer: D. A-T = 2 H-bonds, G-C = 3, fits the helix
Base-pair geometry only works for A-T (2 H-bonds) and G-C (3 H-bonds).
Other combinations have wrong shape or donor/acceptor patterns.
Chargaff's rule (%A = %T, %G = %C) is the empirical confirmation.
Molecular weight and pyrimidine class don't dictate pairing.
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