AP BIOLOGY

Detailed explanation-1: -For example, DNA polymerase III does most of the elongation work, adding nucleotides one by one to the 3’ end of the new and growing single strand.

Detailed explanation-2: -DNA polymerase III starts adding nucleotides to the 3’-OH end of the primer. Elongation of both the lagging and the leading strand continues. RNA primers are removed by exonuclease activity. Gaps are filled by DNA pol I by adding dNTPs.

Detailed explanation-3: -All known DNA polymerases add a deoxyribonucleoside 5′-triphosphate to the 3′ hydroxyl group of a growing DNA chain (the primer strand).

Detailed explanation-4: -DNA polymerase catalyzes the formation of the phosphodiester bond by adding the deoxynucleoside triphosphate onto the growing polynucleotide chain. During this step-wise process, a single pyrophosphate molecule is released every time the chain is elongated by one deoxyribonucleotide.

Detailed explanation-5: -Two molecules of DNA polymerase III bind to the primers on the leading and lagging strands and synthesize new DNA from the 3′ hydroxyls (Fig. 4.5). DNA polymerase cannot synthesize new DNA without a pre-existing 3′-OH. Thus, DNA replication requires an RNA primer to initiate strand formation.