transcription in prokaryotes

Transcription in Prokaryotes MCQ

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There are a total of 22 MCQs on transcription in prokaryotes. All questions have been composed by experts and intended to build the concept.

 

Q1. In bacteria, there are three major types of RNA: mRNA, tRNA and rRNA. All three RNAs are needed to synthesize a protein in a cell. Which of the following statement is true in terms of their functions?

  1. mRNA provides the template for protein synthesis
  2. tRNA brings amino acids and reads the genetic code
  3. rRNA play structural and catalytic role during translation
  4. All of the above

Ans: 4

Q2. In prokaryotes, how many RNA polymerases are present for the formation of mRNA, rRNA, and tRNA?

  1. One type
  2. Two types
  3. Three types
  4. Five types

Ans: 1

In prokaryotes, only one type of RNA polymerase is present for the formation of three types of RNAs. RNA polymerase is made up of 6 subunits (2 alpha, beta, beta prime, omega and sigma). All subunits together are called as holoenzyme. And if sigma factor is removed from the holoenzyme – the remaining subunits are called CORE ENZYME.

Q3. Which of the following RNA is most abundant in a cell?

  1. rRNA
  2. mRNA
  3. tRNA
  4. snRNA

Ans: 1

rRNA is the most abundant in a cell. R stands for rampant meaning lots of. rRNA counts 80% in a cell. On the other hand, mRNA is the most massive RNA – here m stands for massive. Though massive, but very few in number – mRNA is only 5% in a cell.

Q4. Which of the following RNA polymerase is involved in the formation of hnRNA in eukaryotes?

  1. RNA pol I
  2. RNA pol II
  3. RNA pol III
  4. All of the above

Ans: 2

In eukaryotes, three types of RNA polymerases are present. RNA pol I involved in the formation of rRNA; RNA pol II makes hnRNA and RNA pol III makes tRNA.

Q5. What do you mean by heterogenous RNA (hnRNA)?

  1. hnRNA is a type of RNA that is involved in the formation of enzymes
  2. hnRNA is a primary transcript that is involved in the formation of mRNA
  3. hnRNA is a primary transcript that is involved in the formation of rRNA
  4. hnRNA is a primary transcript that is involved in the formation of tRNA

Ans: 2

Q6. Which of the following RNA polymerase is involved in the formation of tRNA and snRNA (small nuclear RNA)?

  1. RNA pol I
  2. RNA pol II
  3. RNA pol III
  4. RNA pol V

Ans: 3

RNA polymerase III is involved in the formation of transfer RNA (tRNA) and small nuclear RNA (snRNA), scRNA (small cytoplasmic RNA) and 5srRNA.

Q7. Which of the following is the function of snRNA?

  1. Involved in splicing
  2. Involved in protein synthesis
  3. Involved in ribosome formation
  4. Involved in DNA synthesis

Ans: 1

Q8. All the ribosomal RNAs are formed by RNA pol I except one. Which of the following rRNA is not formed by RNA polymerase I?

  1. 28srRNA
  2. 5.8srRNA
  3. 18srRNA
  4. 5srRNA

Ans: d

RNA polymerase I forms 18srRNA, 28srRNA, and 5.8srRNA except 5srRNA.

Q9. Which of the following acts as a catalyst in a bacterial cell [CBSE-2011]?

  1. hnRNA
  2. 23s rRNA
  3. 5s rRNA
  4. snRNA

Ans: 3

Q10. Hn-RNA is [Har. PMT-2005]:

  1. Heteronuclear RNA
  2. Homonuclear RNA
  3. Heterogenous RNA
  4. Useful RNA

Ans: 3

During eukaryotic transcription process, hnRNA is formed first, which undergoes post transcriptional modification to form mRNA.

Q11. Select the correct statement:

  1. RNA polymerase I transcribes rRNAs
  2. RNA polymerase II transcribes snRNA
  3. RNA polymerase III transcribes hnRNA
  4. RNA polymerase II transcribes hnRNA

Choose the correct answer:

  1. a and d are correct
  2. b and c are correct
  3. a and b are correct
  4. a and c are correct
  5. a, b, and d are correct

Ans: 1

Q12. Strand of DNA that functions as template for mRNA transcription is:

  1. Coding strand
  2. Non-coding strand
  3. Sense strand
  4. Antisense strand

Choose the correct answer:

  1. a and c are correct
  2. a and d are correct
  3. b and c are correct
  4. b and d are correct

Ans: 4

Q13. What are the different types of ribosomal RNA formed in prokaryotes?

  1. 2
  2. 3
  3. 4
  4. 5

Ans: 2

Three types of ribosomal RNA are formed in prokaryotes. These include 16srRNA, 23srRNA, and 5srRNA.

Q14. In prokaryotic transcription, only one of the strands of a double stranded DNA is involved, why?

  1. If both the strands of DNA form RNA, it will result in the formation of two types of proteins, which will double the amount of proteins formed in the cell from every dsDNA, which will result in increase in complexity of the cellular system
  2. If both the strands form RNA, both RNAs will be complimentary to each other resulting in the formation of double stranded RNA, which cannot be involved in translation
  3. Both a and b
  4. None of the above

Ans: 3

Q15. Which of the following statement is true for the RNA polymerase enzyme subunits?

  1. Alpha subunit scans the DNA for a promoter sequence
  2. The sigma factor binds to the pribnow box and initiate transcription correctly
  3. Beta subunit adds new nucleotides to form a polynucleotide
  4. Beta prime binds to the DNA template
  5. All of the above

Ans: e

Q16. Which of the following sequence is represented by PRIBNOW BOX?

  1. TATAAT
  2. TTGACAT
  3. ATGCAT
  4. GGCCTT

Ans: a

Q17. Which conserved motifs occur in E. coli [DPMT-2007]?

  1. TATA box
  2. CAAT box
  3. Pribnow box
  4. None of the above

Ans: c

Q18. Which of the following event occurs during the transcription initiation process?

  1. RNA polymerase (holoenzyme) joins to the promoter region of the DNA template
  2. Sigma factor is involved in recognizing the promoter region on the DNA template
  3. Sigma factor is responsible for separating the DNA strands so that core enzyme can bind tightly to the DNA in preparation for RNA synthesis
  4. The core enzyme bound to the promoter region starts transcription
  5. All of the above

Ans: e

Once the promoter region is detected by the holoenzyme, the sigma factor opens up the DNA helix for the core enzyme to initiate transcription. And then the sigma factor is released. It is important to note that transcription starts at +1 point, which lies before the protein-coding segment of the gene (usually at the sequence ATG), which is where translation usually starts. Hence the RNA which formed before the ATG sequence is called 5’-untranslated region or 5’ UTR.

Q19. Transcription [DPMT-2005]:

  1. Starts at initiator region and ends at stop region
  2. Starts at operator region and ends at telomeric end
  3. Starts at promoter region and ends at terminator region
  4. Starts at CAA box and ends at TATA box

Ans: c

Q20. Elongation step in the transcription is performed by:

  1. Sigma factor
  2. Holoenzyme
  3. Core enzyme
  4. Alpha subunit of RNA polymerase

Ans: c

Elongation is performed by the core enzyme. After the initiation process, the core enzyme moves on the DNA template strand for RNA synthesis. The core enzyme will unwind the DNA strands to separate template from the non template strand. After unwinding of the helix, RNA synthesis will start leading to the formation of DNA-RNA hybrid. Like DNA replication, here also the substrate is activated from ribonucleoside monophosphate to ribonucleoside triphosphate. The RNA polymerase will continue moving on the DNA template to form RNA till it reaches the termination region.

Q21. Which of the following is responsible for the termination of prokaryotic transcription process?

  1. Alpha subunit of RNA polymerase
  2. Beta subunit of RNA polymerase
  3. Sigma factor of RNA polymerase
  4. Rho factor protein

Ans: d

Rho factor protein is involved in the termination of transcription process. The rho factor helps release the RNA polymerase as well as the newly synthesized RNA strand from the DNA template.

Q22. The enzyme that catalyzes transcription of RNA in bacteria is [Kerela-2015]:

  1. DNA dependent RNA polymerase
  2. RNA polymerase I
  3. DNA polymerase
  4. RNA polymerase II
  5. RNA polymerase III

Ans: a

RNA dependent DNA polymerase is reverse transcriptase.the

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