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

Nucleic acid polymerases are of the following types –

1. DNA polymerase: This enzyme is essential for replication. It uses DNA template to induce polymerisation of deoxynucleotide. Both chains of DNA molecules do not separate together. DNA double helix opens in small parts for replication. The resulting parts are joined with each other by DNA ligase enzyme. DNA polymerase cannot initiate the replication process on its own. It happens with the help of vector at certain sites.
2. RNA polymerase: This is DNA dependent RNA polymerase. It catalyses DNA for transcription of all types of RNA. RNA polymerase temporarily binds with initiation factor or termination factor and initiates or terminates transcription. Apart from DNA dependent RNA polymerase, the following three types of RNA polymerases are found in the nucleus –
   1. RNA Polymerase I: It transcribes ribosomal RNA (r-RNA).
   2. RNA Polymerase II: It transcribes heterogeneous nuclear RNA (hnRNA), the precursor of messenger RNA (m-RNA).
   3. RNA Polymerase III: It is responsible for the transcription of transfer RNA (t-RNA) and small nuclear RNA.