In eukaryotes, which polymerase transcribes the multiple 5S rRNA genes located separately from the main rRNA gene clusters? Pick the correct enzyme.

Introduction / Context:
Eukaryotic ribosomes are assembled from rRNAs transcribed by different enzymes. The large ribosomal RNA precursor (45S) is made by RNA polymerase I, whereas the 5S rRNA is transcribed separately, typically from distinct chromosomal loci.

Given Data / Assumptions:

• 5S rRNA genes are often organized as tandem arrays independent of the 45S rDNA repeats.
• RNA polymerase III specializes in small RNAs including tRNAs and 5S rRNA.

Concept / Approach:
Assign the appropriate transcription machinery based on RNA class: Pol I → 45S rRNA precursor; Pol III → 5S rRNA; Pol II → mRNA. Therefore, the enzyme for 5S rRNA is RNA polymerase III.

Step-by-Step Solution:
Identify target RNA: 5S rRNA.Map to polymerase: Pol III.Exclude Pol I (28S/18S/5.8S precursor) and Pol II (mRNA).

Verification / Alternative check:
Promoter analyses show internal control regions (A- and C-boxes) for Pol III transcription of 5S genes, distinct from Pol I promoters.

Why Other Options Are Wrong:
Pol II makes mRNA; Pol I does not transcribe 5S; DNA polymerase I replicates DNA, not RNA transcription.

Common Pitfalls:
Assuming all rRNAs come from Pol I; 5S is the major exception handled by Pol III.

Final Answer:
RNA polymerase III.