RNA Polymerase (RNAP)

RNA Polymerase (RNAP)

Q. 1 RNA polymerase recognizes? 
 A

Promoter site

 B Initiation site
 C Regulator site
 D Stop site
Q. 1 RNA polymerase recognizes? 
 A

Promoter site

 B Initiation site
 C Regulator site
 D Stop site
Ans. A

Explanation:

(40)        Promoter site REF: Harper 27`h ed p. 349

RNA polymerase has sigma sub unit which recognises promotor nucleotide sequence. It does not require primer and has no proof reading activity

Types:

  1. r RNA
  2. m RNA, mi RNA, Sn RNA
  3. t- RNA, 5s-rRNA, some SnRNA

Q. 2 To initiate transcription RNA polymerase does not require which one of the following:

 A

Template (ds DNA)

 B

Activated precursors (ATP, GTP, UTP, CTP)

 C

Divalent metal ions (Mn2+, Mg2+)

 D

Primer

Q. 2

To initiate transcription RNA polymerase does not require which one of the following:

 A

Template (ds DNA)

 B

Activated precursors (ATP, GTP, UTP, CTP)

 C

Divalent metal ions (Mn2+, Mg2+)

 D

Primer

Ans. D

Explanation:

DNA polymerase can only elongate existing polynucleotide chains, and thus requires a primer. RNA polymerase can initiate RNA synthesis de novo and hence does not require a primer.

Ref: Molecular Biology of the Gene Watson, 2004, Page 376 ;  Lippincott’s Illustrated Q & A Review of Biochemistry by Michael A. Lieberman, Rick Ricer, 2009, Page 294


Q. 3

The sigma (cr) subunit of prokaryotic RNA polymerase:

 A

Binds the antibiotic rifampicin

 B

Is inhibited by a-amanitin

 C

Specifically recognizes the promoter site

 D

Is part of the core enzyme

Q. 3

The sigma (cr) subunit of prokaryotic RNA polymerase:

 A

Binds the antibiotic rifampicin

 B

Is inhibited by a-amanitin

 C

Specifically recognizes the promoter site

 D

Is part of the core enzyme

Ans. C

Explanation:

C i.e. Specifically recognizes the promoter site

Quiz In Between


Q. 4

RNA polymerase does not require :

 A

Template (ds DNA)

 B

Activated precursors (ATP, GTP, UTP, CTP)

 C

Divalent metal ions (Mn2+, Mg2+)

 D

Primer

Q. 4

RNA polymerase does not require :

 A

Template (ds DNA)

 B

Activated precursors (ATP, GTP, UTP, CTP)

 C

Divalent metal ions (Mn2+, Mg2+)

 D

Primer

Ans. D

Explanation:

D i.e. Primer


Q. 5

The drug inhibiting DNA-dependent RNA polymerase in Mycobacteria is –

 A

INH

 B

Rifampicin

 C

Ciprofloxacin

 D

Ethionamide

Q. 5

The drug inhibiting DNA-dependent RNA polymerase in Mycobacteria is –

 A

INH

 B

Rifampicin

 C

Ciprofloxacin

 D

Ethionamide

Ans. B

Explanation:

Ans. is ‘b’ i.e., Rifampicin

Mechanism of action of important antitubercular drugs

o Rifampicin —> Inhibits DNA dependent RNA synthesis by inhibiting RNA polymerase.

o INH  —> Inhibits synthesis of mycolic acid which is a component of mycobacterial cell wall. o Pyrazinamide —> Inhibits synthesis of mycolic acid.

o Streptomycin —> Inhibits protein synthesis (translation).

o Ethambutol —> Inhibits incorporation ofmycolic acid into bacterial cell wall by inhibiting arbinosyltransferase.


Q. 6

RNA polymerase has which activity

 A

Primase

 B

Helicase

 C

Ligase

 D

Topoisomerase

Q. 6

RNA polymerase has which activity

 A

Primase

 B

Helicase

 C

Ligase

 D

Topoisomerase

Ans. A

Explanation:

 

DNA synthesis cannot commence with deoxyribonucleotides because DNA polymerase cannot add a mononucleotide to another mononucleotide.

  • Thus, DNA polymerase cannot initiate synthesis of complementary DNA synthesis strand of DNA on a totally single stranded template.
  • For this, they require RNA primer, which is a short piece of RNA formed by enzyme primase (RNA polymerase) using DNA as a template.
  • RNA primer is then extended by addition of deoxyribonucleotides.
  • Later on, the ribonucleotides of the primer are replaced by deoxyribonucleotides.
  • Primase is actually a DNA primase which has RNA polymerase activity. This DNA primase is also called DNA polymerase.

Quiz In Between



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