Question

Depending upon the chemical nature of the template (DNA or RNA) and the nature of nucleic acids synthesised from it (DNA or RNA), list the types of nucleic acid polymerases.

Answer 1

The types of nucleic acid polymerases required for the synthesis of DNA and RNA are:

1. DNA polymerase I, II, and III: They help in the replication of DNA.
2. RNA-dependent DNA polymerase: It helps in the synthesis of DNA from RNA (reverse transcription).
3. DNA-dependent RNA polymerase: It helps synthesise RNA from DNA (transcription).

In eukaryotes, there are at least three RNA polymerases in addition to those found in cell organelles.

• RNA polymerase I transcribes rRNA (28S, 18S and 5.8S).
• RNA polymerase II transcribes the precursor of mRNA called heterogeneous nuclear RNA (hnRNA).
• RNA polymerase III transcribes tRNA, 5SrRNA and snRNAs.