A Levels Biology (9700)•9700/12/O/N/18
Explanation
Maximum hydrogen bonds assume all G-C base pairs
Steps:
- DNA base pairs form hydrogen bonds: A-T with 2 bonds, G-C with 3 bonds.
- Maximum total requires all 700 base pairs to be G-C.
- Calculate: 700 base pairs × 3 bonds per pair = 2100 bonds.
Why D is correct:
- DNA structure defines G-C pairs with 3 hydrogen bonds each; maximum for 700 pairs is 700 × 3 = 2100.
Why the others are wrong:
- A: Too low; undercounts by halving bonds or pairs.
- B: Assumes 1 bond per base pair, ignoring actual counts.
- C: Assumes all A-T pairs (2 bonds each: 700 × 2 = 1400).
Final answer: D
Topic: Structure of nucleic acids and replication of DNA
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