How do base pairing rules make dna replication possible?

For DNA replication to occur, the two chains that form it must be separated, each with a specific base sequence that serves as a template for the coupling of complementary nitrogen bases, that is, adenine with thymine and cytosine with guanine, attending to the base pairing rules.

Explanation:

Base pairing rules is the way in which nitrogen bases are matched in the double strand of DNA during replication, which occurs by binding a purine with a pyrimidine.

The DNA contains sequences of 4 nitrogen bases, two purines and two pyrimidines. Pyrimidines are cytosine and thymine, while purines are adenine and guanine.   Adenine should bind thymine and cytosine with guanine, according to the rule. When the bases are paired, they form hydrogen bonds between them, two for Adenine-Thymine and three for Cytosine with Guanine.

The relationship between the two strands of DNA is that one complements the other, due to the complementarity of their bases.

DNA replication is semi-conservative, since by separating the two chains one serves as a template for a new chain to be formed, by pairing complementary bases. The final result is two DNA molecules, each with an original chain and new one.

Learn more:

DNA replication link