IMAT 2015 Q38 [Transcription]

In a prokaryote, transcription can occur in which of the following?

  1. cytoplasm
  2. mitochondria
  3. ribosomes

A. 3 only
B. 1 and 3 only
C. 1 only
D. 1 and 2 only
E. 2 only

The answer to this question is choice C.

This is a straightforward question, let us then rationalize each of the choices:

  1. Cytoplasm: This is the only correct answer in terms of prokaryotes. As a reminder, transcription is the process of converting a certain DNA sequence into mRNA, which will be used in protein production later on. This is mediated by the enzyme called RNA polymerase, where the process happens within the cytoplasm in prokaryotes. Do not confuse it with the fact that transcription happens in the nucleus in eukaryotes.

  2. Mitochondria: Keep in mind that this is a question about prokaryotes, thus, any mention of organelle should not be even considered, since prokaryotes lack any membrane-bound organelles in the first place. For clarity sake, in eukaryotes, transcription does NOT happen in mitochondria, as its primary function is oxidative phosphorylation, and is not related to transcription.

  3. Ribosomes: Ribosomes are the RNA-protein cellular machinery involved in the process of translation, and not transcription. Ribosomes, regardless of whether the organism is a prokaryote or eukaryote, are tasked to translate mRNA sequences into protein, thus making this an incorrect consideration.

Thus, with that being said, only choice C is correct.