Which enzyme carries out primer removal in prokaryotic DNA replication via 5' to 3' exonuclease activity?

Which enzyme carries out primer removal in prokaryotic DNA replication via 5' to 3' exonuclease activity?

• A. DNA polymerase II
• B. DNA ligase
• C. DNA polymerase I
• D. DNA polymerase III

Answer: (C)

In prokaryotic DNA replication, RNA primers must be removed and replaced with DNA. The enzyme that handles this task uses 5' to 3' exonuclease activity to chew away the RNA primer from its 5' end while its own polymerase activity fills in the resulting gap with DNA—this coordinated activity is nick translation. That combination is a hallmark of DNA polymerase I, so it’s the enzyme responsible for primer removal in this context. After the primer is replaced, DNA ligase seals the remaining nick. The other enzymes play different roles: DNA polymerase III primarily does the bulk DNA synthesis but doesn’t remove primers with 5' to 3' exonuclease activity; DNA polymerase II is mainly involved in repair; and DNA ligase by itself only seals nicks without primer removal.

In prokaryotic DNA replication, RNA primers must be removed and replaced with DNA. The enzyme that handles this task uses 5' to 3' exonuclease activity to chew away the RNA primer from its 5' end while its own polymerase activity fills in the resulting gap with DNA—this coordinated activity is nick translation. That combination is a hallmark of DNA polymerase I, so it’s the enzyme responsible for primer removal in this context. After the primer is replaced, DNA ligase seals the remaining nick. The other enzymes play different roles: DNA polymerase III primarily does the bulk DNA synthesis but doesn’t remove primers with 5' to 3' exonuclease activity; DNA polymerase II is mainly involved in repair; and DNA ligase by itself only seals nicks without primer removal.