Question 1

Which of the following best describes the role of the sigma factor in bacterial transcription?

Accepted Answer

It helps the core RNA polymerase enzyme detect the promoter, initiating transcription.

Question 2

A mutation in the -10 consensus sequence of a bacterial promoter most likely results in which of the following?

Accepted Answer

Decreased transcription due to reduced sigma factor recognition.

Question 3

Which equation best represents the rate of RNA synthesis during elongation in bacteria?

Accepted Answer

$$v = 45 \, 	ext{bases/sec}$$

Question 4

What is the function of the Shine-Dalgarno sequence in prokaryotic translation?

Accepted Answer

It serves as the ribosome binding site, aligning the ribosome with the start codon.

Question 5

Which of the following is true about the genetic code?

Accepted Answer

There are 64 possible codons, with 61 specifying amino acids and 3 as stop codons.

Question 6

A bacterial cell is exposed to a compound that inhibits DNA topoisomerases. What is the most likely effect on transcription?

Accepted Answer

Positive supercoils ahead of the transcription bubble will accumulate, stalling RNA polymerase.

Question 7

Which of the following best describes the process of coupled transcription and translation in bacteria?

Accepted Answer

Ribosomes begin translating mRNA before transcription is complete.

Question 8

Which enzyme is responsible for attaching the correct amino acid to its corresponding tRNA?

Accepted Answer

Aminoacyl-tRNA synthetase

Question 9

What is the main catalytic activity of the ribosome during protein synthesis?

Accepted Answer

Peptidyltransferase activity, forming peptide bonds between amino acids

Question 10

Which of the following statements about mRNA stability in E. coli is correct?

Accepted Answer

The average half-life for mRNA is 1-3 minutes.

Question 11

Which of the following is NOT a function of small RNA (sRNA) in bacteria?

Accepted Answer

Forming ribosomes

Question 12

What is the role of the 3' (acceptor) end of a tRNA molecule?

Accepted Answer

It binds the amino acid to be added to the growing polypeptide chain.

Question 13

Which of the following best explains why the genetic code is described as 'degenerate'?

Accepted Answer

Multiple codons can encode the same amino acid.

Question 14

Which of the following is a direct consequence of a 'down mutation' in a bacterial promoter consensus sequence?

Accepted Answer

Decreased transcription of the gene.

Question 15

Which of the following correctly matches a ribosomal binding site with its function?

Accepted Answer

E site: binds a tRNA recently stripped of its polypeptide

Question 16

Which of the following is true regarding the evolutionary significance of rRNA sequences?

Accepted Answer

Differences in rRNA sequences increase with evolutionary distance among species.

Question 17

Which of the following best describes the process of transcription termination in bacteria?

Accepted Answer

It can occur via Rho-dependent or Rho-independent mechanisms.

Question 18

Which of the following is a real-life application of understanding the Shine-Dalgarno sequence?

Accepted Answer

Designing antibiotics that block ribosome binding to mRNA in bacteria.

Bacterial Transcription and Translation: Mechanisms and Regulation

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