alleryIn DNA the nitrogen bases are arranged on which side of the sugar-phosphate backbone?
APointing inward, paired by hydrogen bonds
BOn the outside facing the cytoplasm
CWithin the phosphate group
DReplaced by ribose
Answer & Solution
Correct answer: A. Pointing inward, paired by hydrogen bonds
1. The Watson-Crick double helix has two antiparallel sugar-phosphate strands.
2. The nitrogenous bases project inward from each strand toward the centre of the helix.
3. Complementary bases pair via hydrogen bonds: A=T (2 bonds) and G≡C (3 bonds).
_Source: Maharashtra Balbharati Std XII Biology, Ch 4 "Molecular Basis of Inheritance" §4.2_
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