Question

“Coupled transcription-translation” means _, and the coupling contributes to gene expression regulation via ___.

A

transcription can start before the end of translation, lacI repression

B

translation can start before the end of transcription, attenuation

C

translation can start before the end of transcription, CRP activation

D

transcription can start before the end of translation, LacI repression

E

translation can start only after transcription is achieved, attenuation

Which of the following elements can terminate transcription in prokaryotes? It is ___

A

RNA polymerase; cis element

B

TATA box, trans-element

C

Hairpin (stem loop) structure with poly U-tail; trans factor

D

Hairpin (stem loop) structure with poly U-tail, cis element

E

RNA polymerase; trans factor

Which of the following can be used to estimate bacterial cell growth?

A

Plating, CFU counting

B

Counting cells under microscope (e.g. in counting chamber)

C

Turbidity measurements

D

Counting cells using flow cytometry

E

All of the above

Answer 1

Q1. Ans is option B.

Coupling transcription-translation means there is simaltaneous occurance of transcription and translation occurring. Because these two are happening together, one can affect the rate of another. This mechanism helps in providing a way of regulating gene expression known as attenuation. The most common example of which is Trp Operon. Here, translation regulates the structure of RNA, which regulates the transcription level. Attenuation here acts as a dampening factor.

Q2. Ans is option D.

Rho-independent termination of transcription involves a RNA duplex formation by cytosine-guanine residues in the RNA chain, which is followed by a polyuracil chain which binds with adenine by weaker bonds. Various factors like NusA binds to the newly formed duplex RNA and causes separation of RNA from DNA. This mechanism is an example of cis acting RNA regulatory elements. Another example for same kind of element is riboswitches.