GATE 2021 BT – Question 12
The enzyme transcribing eukaryotic genes encoding the precursor of 28S, 18S and 5.8S rRNAs is
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Correct answer: (A) RNA polymerase I
Explanation
Eukaryotes have three nuclear RNA polymerases with different jobs:
- **RNA polymerase I** transcribes the large rRNA precursor (45S pre-rRNA in humans), which is processed into **28S, 18S and 5.8S rRNA**. ✓
- **RNA polymerase II** transcribes mRNA and most small nuclear RNAs and miRNAs.
- **RNA polymerase III** transcribes tRNA, **5S rRNA** and some small RNAs.
(RNA polymerase IV is a plant polymerase that makes siRNAs for silencing.)
Answer **RNA polymerase I** (A).