JEE Advanced 2024 Paper 2 · Q10 · Bond Enthalpy
For a double strand DNA, one strand is given below:
5'—A—G—T—C—A—C—G—T—A—A—G—T—C—3'
The amount of energy required to split the double strand DNA into two single strands is _____ kcal $mol^{-1}$. [Given: Average energy per H-bond for A-T base pair = 1.0 kcal $mol^{-1}$, G-C base pair = 1.5 kcal $mol^{-1}$, and A-U base pair = 1.25 kcal $mol^{-1}$. Ignore electrostatic repulsion between the phosphate groups.]
Reveal answer + step-by-step solution
Correct answer:41
Solution
The given strand has 13 bases: A=4, G=3, T=3, C=3. In the duplex this gives 7 A-T pairs (4 A's + 3 T's pair across to T's/A's on the complementary strand) and 6 G-C pairs (3 G's + 3 C's). Each A-T pair has 2 H-bonds and each G-C pair has 3 H-bonds, so energy = $7 \times 2 \times 1.0 + 6 \times 3 \times 1.5 = 14 + 27 = 41$ kcal $mol^{-1}$.
Want to drill deeper? Open this question inside SolveKar AI and tap "Why?" on any step — the AI Mentor reads your full solution context and explains until it clicks. Download SolveKar AI →