AP BIOLOGY

Detailed explanation-1: -DNA polymerases can only add nucleotides to the 3’ end of an existing DNA strand. (They use the free-OH group found at the 3’ end as a “hook, ” adding a nucleotide to this group in the polymerization reaction.)

Detailed explanation-2: -During elongation, an enzyme called DNA polymerase adds DNA nucleotides to the 3′ end of the template. Because DNA polymerase can only add new nucleotides at the end of a backbone, a primer sequence, which provides this starting point, is added with complementary RNA nucleotides.

Detailed explanation-3: -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-4: -The main function of the third polymerase, Pol III, is duplication of the chromosomal DNA, while other DNA polymerases are involved mostly in DNA repair and translesion DNA synthesis. Together with a DNA helicase and a primase, Pol III HE participates in the replicative apparatus that acts at the replication fork.

Detailed explanation-5: -Primase synthesizes RNA primers complementary to the DNA strand. DNA polymerase starts adding nucleotides to the 3’-OH end of the primer.