Statement I: In eukaryotes, RNA polymerase I transcribes the 28S, 18S and 5.8S rRNAs.
Statement II: In eukaryotes, RNA polymerase I is responsible for the transcription of tRNA, 5S rRNA and snRNAs.
In the light of the above statements, choose the correct answer from the options given below:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Statement I is correct but Statement II is incorrect.
Bacteria have a single DNA-dependent RNA polymerase that makes all types of RNA. Eukaryotes have at least three RNA polymerases in the nucleus, with a clear division of labour: RNA polymerase I makes the large rRNAs, RNA polymerase II makes hnRNA (the precursor of mRNA), and RNA polymerase III makes tRNA, 5S rRNA and snRNAs.
Statement I: In eukaryotes, RNA polymerase I transcribes the 28S, 18S and 5.8S rRNAs. — True. These three rRNAs are the products of RNA polymerase I.
Statement II: In eukaryotes, RNA polymerase I is responsible for the transcription of tRNA, 5S rRNA and snRNAs. — False. tRNA, 5S rRNA and snRNAs (small nuclear RNAs) are made by RNA polymerase III, not RNA polymerase I. The 5S rRNA is the one rRNA that RNA polymerase I does not make.
NCERT Extract:
Types of RNA and the Process of Transcription – “… There is a clear cut division of labour. The RNA polymerase I transcribes rRNAs (28S, 18S, and 5.8S), whereas the RNA polymerase III is responsible for transcription of tRNA, 5srRNA, and snRNAs (small nuclear RNAs). The RNA polymerase II transcribes precursor of mRNA, the heterogeneous nuclear RNA (hnRNA).”