AP BIOLOGY

Detailed explanation-1: -coli polymerase I has 3′ to 5′ as well as 5′ to 3′ exonuclease activity. The 5′ to 3′ exonuclease operates in the direction of DNA synthesis and helps remove RNA primers from Okazaki fragments.

Detailed explanation-2: -DNA polymerases can only make DNA in the 5’ to 3’ direction, and this poses a problem during replication. A DNA double helix is always anti-parallel; in other words, one strand runs in the 5’ to 3’ direction, while the other runs in the 3’ to 5’ direction.

Detailed explanation-3: -Taq DNA polymerase has a domain at its amino terminus (residue 1 to 291) that has a 5’-3’ exonuclease activity, a 3’-5’ exonuclease domain in the middle (residue 292 to 423), and a domain at its C-terminus that catalyzes polymerase reactions.

Detailed explanation-4: -DNA replication takes place at a Y-shaped structure called a replication fork. A self-correcting DNA polymerase enzyme catalyzes nucleotide polymerization in a 5′-to-3′ direction, copying a DNA template strand with remarkable fidelity.