Question

How many types of RNA polymerases exist in cells? Write their names and functions.

Answer 1

Hint: Various RNA polymerases in eukaryotes catalyze the process of transcription and are responsible for the formation of different types of RNA such as ribosomal RNA, micro RNA, nuclear RNA, etc.

Complete answer: RNA polymerase or ribonucleic acid polymerase is an enzyme that synthesizes RNA from a DNA template. It is a multi-subunit enzyme that catalyzes the process of transcription from eukaryotes. The prokaryotic RNA polymerase initiates the process of transcription and has a sigma factor that dissociates the enzyme after the transcription initiation. In prokaryotes, the same RNA is used to catalyze the polymerization of coding and non-coding RNA. Whereas in eukaryotes, different RNA catalyzes the polymerization of coding and non-coding RNA. The various types of RNA polymerases in eukaryotes are as follows-
1. RNA polymerase I- It helps in the polymerization of ribosomal RNA and is involved in more than fifty percent of RNA transcription.
2. RNA polymerase II- It is involved in the transcription of mRNA precursors and forms microRNA and small nuclear RNA.
3. RNA polymerase III- It is mainly involved in the transcription of RNAs that are involved in the normal functioning of a cell such as transfer RNA and ribosomal RNA.
4. RNA polymerase IV and V- They are involved in the formation of small interfering RNA and heterochromatin in the nucleus. They are exclusively found in plants.

Note: Eukaryotes have different types of RNA polymerase that transcribes various genes. RNA polymerase I is involved in the transcription of rRNA genes, RNA polymerase II is involved in transcribing genes for mRNA, miRNA, and snRNA. RNA polymerase III is involved in transcribing genes for tRNA and 5S rRNA genes.