Question

The 3' -> 5' exonuclease activities of DNA polymerases read nascent strands as they are synthesized, removing any mispaired nucleotides at the 3 termini of primer strands. This action is known as:

Answer 1

The 3' -> 5' exonuclease activity of DNA polymerases is known as proofreading, and it ensures the accuracy of DNA replication by removing mispaired nucleotides. DNA polymerase I is particularly important for removing RNA primers and replacing them with DNA nucleotides, and DNA ligase seals these fragments together.

Step-by-step explanation:

The 3' -> 5' exonuclease activity of DNA polymerases refers to the proofreading function of these enzymes during DNA replication. As new nucleotides are added in the 5' to 3' direction, the polymerase checks the pairing of the newly added base with the base in the template strand.

If a mispairing is detected, the polymerase will remove the incorrect nucleotide using its 3' -> 5' exonuclease activity. This correctness check is crucial for maintaining the integrity of the DNA.

The DNA polymerase I enzyme, in addition to this proofreading function, also has a 5' exonuclease activity that plays a role in removing the RNA primer from the Okazaki fragments on the lagging strand of the replication fork, replacing them with DNA nucleotides.

The DNA ligase enzyme then seals the gaps between these fragments to form a continuous DNA strand. This coordinated activity ensures the high fidelity of DNA replication and repair.