Question

Which of the following comparisons of prokaryotic transcription and eukaryotic transcription is incorrect?

	Prokaryotic transcription	Eukaryotic transcription
(a)	Transcriptional unit has only one gene	Transcriptional unit has one or more genes
(b)	Occurs in the cytoplasm	Occurs in the nucleus
(c)	A single RNA polymerase synthesises all the three types of RNA	The RNA polymerase I, II and III synthesise rRNA, mRNA and tRNA respectively
(d)	Coupled-transcription translation is the rule	Coupled transcription translation is notpossible

• A. (a)
• B. (b)
• C. (c)
• D. (d)

Answer 1

Answer: (A)

(a)

Prokaryotic vs. Eukaryotic Transcription:

Prokaryotes only contain three different promoter elements: -10, -35 promoters, and upstream elements. Eukaryotes contain many different promoter elements: TATA box, initiator elements, downstream core promoter element, CAAT box, and the GC box to name a few. Eukaryotes have three types of RNA polymerases, I, II, and III, and prokaryotes only have one type. Eukaryotes form an initiation complex with the various transcription factors that dissociate after initiation is completed. There is no such structure seen in prokaryotes. Another main difference between the two is that transcription and translation occur simultaneously in prokaryotes and in eukaryotes the RNA is first transcribed in the nucleus and then translated in the cytoplasm. RNAs from eukaryotes undergo post-transcriptional modifications including capping, polyadenylation, and splicing. These events do not occur in prokaryotes. mRNAs in prokaryotes tend to contain many different genes on a single mRNA meaning they are polycistronic. Eukaryotes contain mRNAs that are monocistronic. Termination in prokaryotes is done by either rho-dependent or rho-independent mechanisms. In eukaryotes, transcription is terminated by two elements: a poly(A) signal and a downstream terminator sequence.

So, the correct answer is '(a)'.