Concept 6 Review

DNA Base Pairing

A-T and G-C base pairs allow the specific interation of nucleotides on different DNA strands.

The purine and pyrimidine bases in DNA can associate together by forming hydrogen bonds.

Most pairings produce only a single hydrogen bond at a time, but two types of base pairings allow for multiple hydrogen bonds. When A and T are brought into close contact, two hydrogen bonds can form simultaneously. When G and C are brought into close contact, three simultaneous hydrogen bonds can form.

The overall bond strength of many hydrogen bonds is additive. In zipper-like fashion, the presence of multiple A-T and G-C base pairs bonds the two strands of DNA tightly together.