For a double-stranded DNA, one strand is given below: ...

The correct numerical answer is 41. Click to view the complete step-by-step calculation.

JEE Advanced 2024 Paper 2 Chemistry Question 10 Solution

Identify the number of base pairs in the double-stranded DNA based on the given sequence: $5' \text{- A G T C A C G T A A G T C - } 3'$ .
Count of A-T pairs: The sequence contains A and T at positions 1, 3, 5, 8, 9, 10, 12. There are 7 A-T base pairs. Each A-T pair has 2 Hydrogen bonds.
Count of G-C pairs: The sequence contains G and C at positions 2, 4, 6, 7, 11, 13. There are 6 G-C base pairs. Each G-C pair has 3 Hydrogen bonds.
Energy calculation for A-T pairs: $7 \text{ pairs} \times 2 \text{ H-bonds/pair} \times 1.0 \text{ kcal mol}^{-1}/\text{H-bond} = 14.0 \text{ kcal mol}^{-1}$ .
Energy calculation for G-C pairs: $6 \text{ pairs} \times 3 \text{ H-bonds/pair} \times 1.5 \text{ kcal mol}^{-1}/\text{H-bond} = 27.0 \text{ kcal mol}^{-1}$ .
Total energy $= 14.0 + 27.0 = 41.0 \text{ kcal mol}^{-1}$ .