DNA polymerases have which true property?

DNA polymerases have which true property?

• A. They can begin synthesis on a template without a primer.
• B. They degrade RNA primers.
• C. They ligate Okazaki fragments.
• D. They can only add nucleotides to the 3' end.

Answer: (B)

DNA polymerases are responsible for building new DNA by adding nucleotides to a preexisting 3' end, and in bacteria a key supporting role is their ability to remove RNA primers. DNA polymerase I has a 5' to 3' exonuclease activity that specifically degrades RNA primers that were laid down to start synthesis. This allows the RNA primer to be removed and the resulting gap to be filled with DNA, a process known as nick translation during Okazaki fragment processing. That primer-removal activity is a true and important property of DNA polymerases in the replication context. The other statements don’t capture a universal function: they cannot start synthesis on a template without a primer, because primer is required to provide a 3'OH for extension; ligation of Okazaki fragments is done by DNA ligase, not polymerase; and saying they can only add nucleotides to the 3' end is overly absolute since polymerases also possess exonuclease activities that can remove nucleotides during proofreading or primer removal in some systems.

DNA polymerases are responsible for building new DNA by adding nucleotides to a preexisting 3' end, and in bacteria a key supporting role is their ability to remove RNA primers. DNA polymerase I has a 5' to 3' exonuclease activity that specifically degrades RNA primers that were laid down to start synthesis. This allows the RNA primer to be removed and the resulting gap to be filled with DNA, a process known as nick translation during Okazaki fragment processing. That primer-removal activity is a true and important property of DNA polymerases in the replication context.

The other statements don’t capture a universal function: they cannot start synthesis on a template without a primer, because primer is required to provide a 3'OH for extension; ligation of Okazaki fragments is done by DNA ligase, not polymerase; and saying they can only add nucleotides to the 3' end is overly absolute since polymerases also possess exonuclease activities that can remove nucleotides during proofreading or primer removal in some systems.