In eukaryotic cells, where are ribosomal RNA (rRNA) transcripts synthesized and assembled with ribosomal proteins into pre-ribosomal subunits?
Answer and explanation
Correct answer: B. Nucleolus
- Step 1: Identify the subnuclear structure dedicated to ribosome biogenesis.
- Step 2: The nucleolus is a dense non-membrane-bound nuclear region where RNA polymerase I transcribes rRNA genes and combines them with imported proteins to assemble the 40S and 60S ribosomal subunits.
Answer
Nucleolus.
Why not the others: Peroxisomes break down fatty acids; centrosomes organize microtubules; rough ER is the site of membrane and secretory protein translation, not subunit assembly.
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