Читать книгу Cell Biology - Stephen R. Bolsover - Страница 62

A hydrogen bond forms when a hydrogen atom is shared. The hydrogen bonds in an A–T and a G–C base pair (Figure 3.4) form when the hydrogen attached to a nitrogen in one base gets close to an electron‐grabbing oxygen or nitrogen in the other base of the pair. The hydrogen bonds formed between the base pairs hold the DNA helix together. The three hydrogen bonds formed between G and C produce a relatively strong base pair. Because only two hydrogen bonds are formed between A and T, this weaker base pair is more easily broken. The difference in strengths between a G–C and an A–T base pair is important in the initiation of DNA replication (page 51) and in the initiation and termination of RNA synthesis (page 69).