Question

Eukaryotic cells have multiple RNA polymerases. Which of the following RNA genes is not transcribed by RNA polymerase I.

- 5.8S RNA

- 18S RNA

- 5S rRNA

- none of the others

- 28S RNA

Answer 1

The 5S rRNA gene is not transcribed by RNA polymerase I but by RNA polymerase III. RNA polymerase I transcribes 18S, 5.8S, and 28S rRNA components. Eukaryotic cells have three RNA polymerases, each responsible for different sets of RNA genes.

Step-by-step explanation:

The 5S rRNA gene is not transcribed by RNA polymerase I in eukaryotic cells. Instead, it is transcribed by RNA polymerase III. RNA polymerase I is responsible for transcribing the 18S, 5.8S, and 28S ribosomal RNA (rRNA) components, which are parts of the larger 45S precursor transcript. RNA polymerase II, on the other hand, is in charge of all protein-coding genes (mRNAs).

The initiation of transcription involves several transcription factors that bind to complex promoter sequences which are usually located upstream of the genes being copied. The unique aspect of RNA polymerase III is that it binds to an internal promoter within the 5S rRNA gene, contrary to the upstream location typically found for other genes.