Question

For a double strand DNA, one strand is given below:

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.]

Answer 1

Correct Answer: 41

Calculation of Energy Required for DNA Denaturation 

The given DNA sequence contains:

• Seven adenine-thymine (A-T) base pairs.
• Six guanine-cytosine (G-C) base pairs.

Step 1: Energy Contributions

Each A-T pair contributes 2 hydrogen bonds, each requiring 1 kcal of energy:

\[ 7 \times 2 \times 1 = 14 \, \text{kcal} \]

Each G-C pair contributes 3 hydrogen bonds, each requiring 1.5 kcal of energy:

\[ 6 \times 3 \times 1.5 = 27 \, \text{kcal} \]

Step 2: Total Energy Required

\[ \text{Total Energy} = 14 + 27 = 41 \, \text{kcal} \]

Final Answer:

The total energy required for DNA denaturation is 41 kcal.