$ The two strands of DNA run in an antiparallel directions
DNA is formed of Deoxyribose sugar. Phosphorus and nitrogen bases called purines and pyrimidines.

Options

A. If both As and R are correct and R is correct explanation of As
B. If both As and R are correct but R is not correct explanation of As
C. If As is correct, R is wrong
D. If both As and R are wrong.

Answer

To analyze the assertion and reason provided in the question, we can break down the solution into several steps:

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "the two strands of DNA run in an antiparallel direction."
- This means that one strand runs in the 3' to 5' direction while the other runs in the 5' to 3' direction.

2. **Evaluating the Assertion**:
- The assertion is correct. In DNA, the antiparallel arrangement is crucial for the base pairing between the strands. This orientation allows the nitrogenous bases to pair correctly (A with T and G with C).

3. **Understanding the Reason**:
- The reason provided states that "DNA is formed of deoxyribose sugar, phosphorus, and nitrogen bases called purines and pyrimidines."
- This describes the components of DNA: the sugar (deoxyribose), the phosphate group, and the nitrogenous bases (purines: adenine and guanine; pyrimidines: cytosine and thymine).

4. **Evaluating the Reason**:
- The reason is also correct as it accurately describes the structure of DNA. However, it does not explain why the strands are antiparallel.

5. **Conclusion**:
- Both the assertion and reason are correct statements. However, the reason does not serve as a correct explanation for the assertion. Therefore, the correct answer is that both the assertion and reason are correct, but the reason is not the correct explanation of the assertion.

### Final Answer:
Both assertion and reason are correct, but the reason is not the correct explanation of the assertion.

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