What is the principle of complementary base pairing in DNA?

• A. Pairing of nucleotides without specificity
• B. Specific pairing of adenine with thymine and guanine with cytosine
• C. Random pairing of DNA sequences
• D. Pairing of phosphate groups with sugar molecules

Answer: (B)

The principle of complementary base pairing in DNA refers to the specific way in which nucleotide bases pair with one another to form the double helix structure of DNA. In this context, adenine (A) pairs specifically with thymine (T), and guanine (G) pairs specifically with cytosine (C). This pairing occurs due to the ability of A and T to form two hydrogen bonds with each other, while G and C form three hydrogen bonds. This specificity is crucial because it ensures accurate replication of DNA during cell division and proper transcription of genetic information, which ultimately leads to protein synthesis.

Moreover, the complementary base pairing contributes to the stability of the DNA molecule, as the consistent width of the double helix and the hydrogen bonding between complementary bases facilitate the coiling and compact structure essential for genetic information storage. This principle underlies many fundamental processes in molecular biology, including DNA replication, where each strand serves as a template for the formation of a new complementary strand.

The other options do not accurately describe the specificity required for base pairing in DNA structure and function.