Final answer:
The two complementary base pairs in DNA, according to Chargaff's rule, are adenine (A) paired with thymine (T), and guanine (G) paired with cytosine (C). They are bonded together through hydrogen bonds, where A and T form two bonds, and C and G form three bonds, ensuring the structural integrity and accurate replication of DNA.
Step-by-step explanation:
Complementary Base Pairs in DNA
According to Chargaff's rule, the complementary base pairs in DNA are adenine (A) with thymine (T), and guanine (G) with cytosine (C). These base pairs are complementary because they always pair together within the DNA molecule. The pairing is a result of specific hydrogen bonding patterns: A and T form two hydrogen bonds between them, whereas C and G form three hydrogen bonds. This observation is key to understanding the structure of DNA and how it ensures the correct replication of genetic information.
Base-Pairing Rules dictate that for a given sequence of DNA, if one strand reads ATGCCAGT, the complementary strand will read TACGGTCA. This characteristic ensures that the two chains of the DNA double helix are complementary to each other. Complementary base pairs are a fundamental concept in molecular biology, as they allow the DNA to maintain its structure and carry genetic information accurately from one generation to the next.
Erwin Chargaff's research was crucial in aiding Watson and Crick to model the DNA double helix structure. Chargaff noted consistent patterns across different species, such that the ratio of adenine to thymine and guanine to cytosine was always approximately one. This concept, together with the knowledge that base pairs are formed between a purine (A or G) and a pyrimidine (T or C), helped in understanding the pairing mechanism and the antiparallel nature of the DNA strands in the helix structure.