Question

Assertion (A): The two strands of DNA are complementary to each other.
Reason (R): The hydrogen bonds are formed between specific pairs of bases.

• A. Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).
• B. Both Assertion (A) and Reason (R) are true, but Reason (R) is not the correct explanation of the Assertion (A).
• C. Assertion (A) is true, but Reason (R) is false.
• D. Assertion (A) is false, but Reason (R) is true.

Hint:

In DNA, hydrogen bonds form only between specific base pairs: adenine pairs with thymine and guanine pairs with cytosine, so the Reason is true.

Answer 1

The Correct Option is A

Step 1: Check the Reason.
In DNA, hydrogen bonds form only between specific base pairs: adenine with thymine and guanine with cytosine. So the Reason is true.

Step 2: Meaning of complementary strands.
Because each base can pair only with its specific partner, the order of bases on one strand fixes the order on the other strand.

Step 3: Judge the Assertion.
This base pairing is exactly why the two strands are complementary, so the Assertion is true.

Step 4: Link them.
The complementary nature is a direct result of the specific hydrogen bonded base pairing.

Step 5: Conclusion.
Both are true and the Reason correctly explains the Assertion.

Answer: Both Assertion and Reason are true and Reason is the correct explanation of the Assertion (Option 1).