Question

What is synthesized by RNA polymerase II?
A. rRNA sequence
B. Prokaryotic rRNA
C. Eukaryotic mRNA
D. Prokaryotic tRNA

Answer 1

Hint: Transcription is the process of the creation of a new RNA strand from an existing strand of DNA. Several enzymes are needed for transcription. One such enzyme is RNA polymerase. There is only one RNA polymerase in prokaryotes, whereas, there are different RNA polymerases in eukaryotes with different functions.

Complete answer:
Transcription in Prokaryotes:
It occurs in the cytoplasm of the cell with the help of the transcription enzymes. The transcription enzyme is the DNA-dependent RNA polymerase. There is a single type of RNA polymerase found in the prokaryotic cells. It transcribes all types of RNAs like mRNA, tRNA, and rRNA. All these three RNAs are required to synthesize the proteins within the cell.
Transcription in Eukaryotes:
In eukaryotes, there are three kinds of transcription enzymes. These are the RNA polymerases found in the nucleus other than the RNA polymerase found in the cell organelles. All these RNA polymerases have a division of labor. The following are the three kinds of RNA polymerases found in eukaryotes along with their functions.
1. RNA polymerase I – It helps in the \[5.8S\], 18S, and 28S rRNA synthesis.
2. RNA polymerase II – It helps in the synthesis of the HnRNA (heterogeneous nuclear RNA), and mRNA.
3. RNA polymerase III – It helps in the synthesis of the tRNA, ScRNA, rRNA, and snRNA (small nuclear RNA).
-The nascent RNA that is synthesized by the RNA polymerase II is called HnRNA or the primary transcript. The primary transcript consists of both the unwanted base sequences known as introns which are alternated with the user base sequences called the exons. The primary transcript is converted into the functional mRNA after the post-transcriptional processing. Thus, RNA polymerase II synthesizes eukaryotic mRNA.
Hence, the correct answer is option (C).

Note: The RNA polymerase is a Holoenzyme. This means that it is a biochemically active compound which is a combination of the enzyme and coenzyme. It is made up of polypeptides \[\left( {{\alpha _2}\beta \beta '\omega } \right)\sigma \]. Here \[\left( {{\alpha _2}\beta \beta '\omega } \right)\] is the core enzyme and \[\sigma \] is the co-enzyme.