Which enzyme is described as the main DNA polymerase that copies the template strand in prokaryotes?

• A. DNA Polymerase III
• B. DNA Polymerase I
• C. Helicase
• D. Primase

Answer: (A)

DNA polymerase III is the main enzyme that copies the template strand in prokaryotes. It’s part of a highly coordinated holoenzyme with high processivity, thanks to the sliding clamp that grips the DNA and lets Pol III add thousands of nucleotides before it falls off. It synthesizes DNA in the 5' to 3' direction and handles both strands: on the leading strand it runs continuously, while on the lagging strand it creates Okazaki fragments that are later processed. Primers are laid down by primase, and DNA polymerase I removes those RNA primers and fills in the gaps with DNA, with DNA ligase sealing the nicks. Helicase unwinds the double helix, but the bulk of DNA synthesis—the main copying function—belongs to DNA polymerase III, aided by its proofreading activity to correct mistakes.