AP BIOLOGY

Detailed explanation-1: -Because of its 5′ to 3′ exonuclease activity, DNA polymerase I removes RNA primers and fills the gaps between Okazaki fragments with DNA.

Detailed explanation-2: -Exonucleases can act as proofreaders during DNA polymerisation in DNA replication, to remove unusual DNA structures that arise from problems with DNA replication fork progression, and they can be directly involved in repairing damaged DNA.

Detailed explanation-3: -DNA polymerase I is a single polypeptide chain with 928 amino acids and molecular weight of 109 kDa. It has three sites, which provide three distinct catalytic activities: 3′ to 5′ exonuclease, 5′ to 3′ exonuclease, and 5′ to 3′ polymerase.

Detailed explanation-4: -Exonucleases can act as proof-readers during DNA polymerization in DNA replication. They work by scanning along the newly synthesized strand directly behind the DNA polymerase. If the last nucleotide added is mismatched, it will be removed by the exonuclease.

Detailed explanation-5: -The flap pathway and the exonuclease pathway for the removal of RNA-DNA primers from Okazaki fragments are shown. i, the RNase H2-and Exo1-mediated exonuclease pathway. The RNA-DNA primers are directly hydrolyzed by RNase H2 and Exo1.