Question

RNA polymerase II differs from RNA polymerase I and III by having?

1) fewer amino acids at the N-terminus
2) additional amino acids at the N-terminus
3) fewer amino acids at the C-terminus
4) additional amino acids at the C-terminus
5) individual amino acids, but all three RNA polymerases are the same size

Answer 1

RNA polymerase II has additional amino acids at the C-terminus, which is known as the C-terminal domain (CTD), setting it apart from RNA polymerase I and III, making option 4 the correct answer.

Step-by-step explanation:

In eukaryotic cells, there are three main types of RNA polymerases each responsible for synthesizing different types of RNA. RNA polymerase II differs from RNA polymerase I and III in various aspects, including the area of functionality and structural components. One key difference is found in their C-terminal domain (CTD).

RNA polymerase II has a unique C-terminal domain that consists of a long, repetitive sequence of amino acids which is crucial for its function in mRNA processing. Therefore, the correct answer to the question 'RNA polymerase II differs from RNA polymerase I and III by having?' is option 4, 'additional amino acids at the C-terminus'.

The unique extension at the C-terminal domain of RNA polymerase II is used for several critical post-transcriptional modifications, such as the addition of the 5' cap and the 3' poly-A tail, as well as mRNA splicing.

RNA polymerase II itself transcribes mRNA, while RNA polymerases I and III are responsible for the synthesis of rRNA and tRNAs respectively. Understanding this distinction is fundamental for comprehending the role and function of the different RNA polymerases in eukaryotic transcription.