Final answer:
In DNA, nitrogen bases pair specifically: adenine (A) with thymine (T) and guanine (G) with cytosine (C), due to hydrogen bonding which preserves genetic information during cell replication.
Step-by-step explanation:
According to base pairing rules, in the structure of DNA, the nitrogen bases pair together in a very specific way due to hydrogen bonding. Adenine (A) pairs with thymine (T), while guanine (G) pairs with cytosine (C). This A-T and G-C pairing is consistent due to the complimentary nature of the bases where adenine and thymine form two hydrogen bonds between them, and cytosine and guanine form three hydrogen bonds. This complementary base pairing is crucial in preserving genetic information during cell division or mitosis.
Furthermore, the pairing between a purine (A or G) and a pyrimidine (T or C) keeps a uniform distance between the base pairs, maintained by the electrostatic force, which is significant thanks to the proximity of the bases within the DNA helix. These pairings are integral in maintaining the double-helical structure proposed by Watson and Crick, contributing to the stability of DNA's molecular structure and the precision in genetic information transfer.