Question

The enzyme that transcribes the eukaryotic genes encoding precursor ribosomal RNAs (pre-rRNAs) of 28S, 18S and 5.8S rRNAs is

• A. RNA polymerase I
• B. RNA polymerase II
• C. RNA polymerase III
• D. RNA polymerase IV

Hint:

Remember: RNAP I → rRNA, RNAP II → mRNA, RNAP III → tRNA & 5S rRNA.

Answer 1

The Correct Option is A

Eukaryotes use different RNA polymerases for different RNA classes.
RNA polymerase I transcribes the 45S pre-rRNA, which is later processed into 28S, 18S, and 5.8S rRNAs.
These rRNAs form the main structural components of ribosomes.
RNA polymerase II makes mRNA, and RNA polymerase III makes tRNA and 5S rRNA, so they are not correct here.
RNA polymerase IV is found only in plants and is unrelated to rRNA synthesis.
Thus, the correct enzyme is RNA polymerase I.