DNA replication

DNA replication begins with the "unzipping" of the parent molecule as the hydrogen bonds between the base pairs are broken. Once exposed, the sequence of bases on each of the separated strands serves as a template to guide the insertion of a complementary set of bases on the strand being synthesized.

The new strands are assembled from deoxynucleoside triphosphates. Each incoming nucleotide is covalently linked to the "free" 3' carbon atom on the pentose (figure) as the second and third phosphates are removed together as a molecule of pyrophosphate (PPi). The nucleotides are assembled in the order that complements the order of bases on the strand serving as the template. Thus each C on the template guides the insertion of a G on the new strand, each G a C, and so on. When the process is complete, two DNA molecules have been formed identical to each other and to the parent molecule.