Which enzyme removes RNA primers during DNA replication in many bacteria?

• A. Helicase
• B. DNA ligase
• C. RNA polymerase
• D. DNA polymerase I (with 5' to 3' exonuclease activity)

Answer: (D)

In bacterial DNA replication, primers are RNA segments that must be removed and replaced with DNA before the strand is finished. DNA polymerase I is responsible for this primer removal because it has a 5' to 3' exonuclease activity that digests RNA in the primer. As it removes the RNA primer, its own polymerase activity fills the resulting gap with DNA. After that, DNA ligase seals the remaining nick to complete the strand. The other enzymes play different roles: helicase unwinds the DNA, RNA polymerase (primase) creates the RNA primers, and DNA ligase only seals the final backbone after replacement.