Correct Option (A):
The complementary nature of the two DNA strands is fundamental to its role in genetic information storage and transmission. Due to specific base pairing rules (adenine with thymine, guanine with cytosine), each strand serves as a template for the synthesis of a new complementary strand during DNA replication. This mechanism ensures precise duplication of the genetic code, allowing for faithful inheritance of genetic information from parent to offspring across generations.
Incorrect Options:
- Option B (Double helix): While the double helical structure provides significant stability to the DNA molecule, which is crucial for preserving genetic integrity, it is the complementary base pairing within this structure that directly facilitates accurate replication and thus information transmission.
- Option C (Number of base-pairs per turn): This refers to a specific structural dimension of the DNA helix. It is a characteristic feature of the molecule's physical arrangement but does not directly explain its capacity for information storage or its mechanism of transmission.
- Option D (Sugar-phosphate backbone): The sugar-phosphate backbone forms the structural framework of each DNA strand, providing strength and rigidity. However, it is the sequence of nitrogenous bases attached to this backbone, and their complementary pairing, that carries the genetic information and enables its replication, not the backbone itself.