Hydrogen bonds in DNA base pairing

Steps:

• Examine the DNA section to identify complementary base pairs (A-T and G-C).
• Count A-T pairs (each forms 2 hydrogen bonds) and G-C pairs (each forms 3 hydrogen bonds).
• Multiply: 2 × (number of A-T pairs) + 3 × (number of G-C pairs).
• For this section with 10 A-T and 6 G-C pairs, total is 20 + 18 = 38.

Why C is correct:

• DNA structure dictates A-T pairs form 2 H-bonds and G-C pairs form 3, per Watson-Crick model; 10×2 + 6×3 = 38.

Why the others are wrong:

• A: Underestimates by ignoring extra bond in each G-C pair.
• B: Assumes all pairs are A-T (2 bonds each for 16 pairs).
• D: Overcounts, possibly assuming 3 bonds for all 16 pairs.

Final answer: C