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.

Hint:

Remember the Chargaff's rule: In a DNA molecule, the amount of Adenine equals Thymine and the amount of Guanine equals Cytosine.

Answer 1

Step 1: Conceptual Overview:
The double-helical structure of DNA is stabilized by specific interactions between nitrogenous bases on opposing strands. These interactions are crucial for maintaining the integrity of the DNA molecule.
Step 2: Detailed Explanation:
1. Assertion Analysis: DNA consists of two polynucleotide chains that run in opposite directions. These chains are complementary rather than identical, meaning the sequence of bases in one strand dictates the sequence in the other. This complementarity is fundamental to the structure and function of DNA. (True)
2. Reason Analysis: The complementarity of the strands is due to specific base pairing: Adenine (A) always pairs with Thymine (T) through two hydrogen bonds, while Guanine (G) pairs with Cytosine (C) through three hydrogen bonds. This specific pairing ensures that the two strands of DNA are complementary to each other. (True)
3. Relationship: The specificity of base pairing (A-T and G-C) allows one strand to serve as a template for the other, meaning the two strands are complementary. This relationship between the assertion and the reason is clear: the reason correctly explains why the assertion is true.
Step 3: Final Conclusion:
Both Assertion (A) and Reason (R) are true, and Reason (R) provides the correct explanation for Assertion (A).