DNA polymerase I, from E. coli, has three different catalytic sites. Which of the following is NOT one of them?

A. RNA-dependent RNA polymerase

B. RNA-dependent DNA polymerase

C. DNA-dependent RNA polymerase

D. DNA-dependent DNA polymerase

RNA-dependent RNA polymerase.

Explanation:

DNA polymerase I is present in E. coli that are responsible for the prokaryotic DNA replication. The DNA polymerase I was discovered by Arthur Kornberg. This enzyme is coded by the gene polA.

DNA polymerase I has the activites of DNA-dependent RNA polymerase, DNA-dependent DNA polymerase and RNA-dependent DNA polymerase. The RNA-dependent RNA polymerase is generally present in the reverse transcriptase in case of viruses only. RNA-dependent RNA polymerase catalytic site is not present in DNA polymerase I.

Thus, the correct answer is option (1).