In a human cell, which RNA polymerase transcribes the 45S precursor that is processed into 18S, 5.8S and 28S rRNA?
- A RNA polymerase III
- B RNA polymerase II
- C RNA polymerase I ✓
- D Mitochondrial RNA polymerase
Correct answer: C. RNA polymerase I
Explanation
RNA polymerase I sits in the nucleolus and transcribes the single large 45S pre-rRNA transcript containing the 18S, 5.8S and 28S sequences. Polymerase II produces mRNA, most miRNA and snRNA, and polymerase III produces tRNA, 5S rRNA and other small RNAs. The best distractor is polymerase III because it also makes an rRNA species, but only the small cytoplasmic 5S rRNA, never the nucleolar 45S precursor.
Reference: Lippincott's Illustrated Reviews: Biochemistry, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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