Two samples of DNA, A and B have melting points 340K and 350 K respectively. This is because

Options

A. B has more GC content than A.
B. A has more GC content than B
C. A has more AT content than B
D. Both have same AT content

Answer

To solve the question regarding the melting points of two DNA samples, A and B, we need to understand the relationship between the composition of the DNA (specifically the GC and AT content) and the melting point.

### Step-by-Step Solution:

1. **Understand DNA Structure**: DNA is made up of two strands that are held together by base pairs. The base pairs consist of adenine (A) paired with thymine (T), and guanine (G) paired with cytosine (C).

2. **Hydrogen Bonds**: The bonding between these base pairs is crucial. A-T pairs are held together by two hydrogen bonds, while G-C pairs are held together by three hydrogen bonds. This means that G-C pairs are more stable and stronger than A-T pairs.

3. **Melting Point Concept**: The melting point of DNA refers to the temperature at which the two strands of the DNA double helix separate. Higher melting points indicate stronger interactions between the strands.

4. **Comparison of Samples A and B**: Given that sample A has a melting point of 340 K and sample B has a melting point of 350 K, we can infer that sample B has stronger bonding due to a higher GC content.

5. **Conclusion**: Since sample B has a higher melting point, it must contain more G-C base pairs compared to sample A. Therefore, the correct reason for the difference in melting points is that sample B has more GC content than sample A.

### Final Answer:
**B has more GC content than A.**

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