Question

Which of the following does not occur in prokaryotic gene expression, but does in eukaryotic gene expression?

A. RNA polymerase binds to the promoter.
B.RNA polymerase requires a primer to elongate the molecule.
C. mRNA, tRNA, and rRNA are transcribed.
D. A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end.
E. Transcription can begin as soon as translation has begun even a little.

Answer 1

The event that occurs in eukaryotic but not in prokaryotic gene expression is the addition of a poly-A tail and a 5' cap to the mRNA transcript. Eukaryotic transcription involves RNA polymerase II and additional transcription factors, whereas prokaryotic RNA polymerase can initiate transcription without these factors.

Step-by-step explanation:

The process that does not occur in prokaryotic gene expression but does occur in eukaryotic gene expression is D. A poly-A tail is added to the 3' end of an mRNA and a cap is added to the 5' end. In prokaryotic cells, the mRNA transcript is usually polycistronic and does not undergo such modifications. In contrast, eukaryotic mRNA transcripts undergo several processing steps, including the addition of a 5' cap and a 3' poly-A tail; these modifications are critical for mRNA stability and the regulation of its translation into proteins.

Differences between prokaryotic and eukaryotic gene expression are substantial. In eukaryotes, polymerase II is primarily responsible for the transcription of mRNA and is aided by additional transcription factors for initiation. Unlike prokaryotic RNA polymerase, which can bind directly to the promoter, eukaryotic RNA polymerase requires other proteins to facilitate transcription initiation. Furthermore, eukaryotic mRNAs are usually monocistronic, whereas prokaryotic mRNAs can encode multiple polypeptides.