Question

Which of the following rRNA components originates from a separate gene transcript rather than as a cleaved product of a long single precursor rRNA transcript?

1) Prokaryotic 16S rRNA
2) Prokaryotic 23S rRNA
3) Eukaryotic 18S rRNA
4) Eukaryotic 5.8S rRNA
5) Eukaryotic 5S rRNA

Answer 1

The eukaryotic 5S rRNA is the rRNA component that is transcribed separately by RNA Polymerase III from a distinct gene transcript and not derived from the longer 45S precursor transcript.

Step-by-step explanation:

The rRNA component that originates from a separate gene transcript rather than a cleaved product of a long single precursor rRNA transcript is the eukaryotic 5S rRNA. In eukaryotes, the 45S precursor rRNA is processed to produce the 18S, 28S, and 5.8S rRNAs, while the 5S rRNA is transcribed separately by RNA Polymerase III. This transcription occurs through an internal promoter within the rRNA sequence, not an upstream promoter, distinguishing the 5S rRNA from the other eukaryotic rRNAs that are transcribed by RNA Polymerase I and originate from a longer precursor transcript.