Question 1

Which enzyme is responsible for introducing negative supercoils into bacterial DNA, and what is the biological significance of this process?

Accepted Answer

DNA gyrase; it compacts DNA and facilitates replication and transcription

Question 2

A bacterial cell is exposed to a high temperature environment. Which DNA supercoiling state would be most beneficial for maintaining DNA stability, and why?

Accepted Answer

Positive supercoiling, because it prevents DNA melting

Question 3

Which of the following statements best distinguishes plasmids from viruses?

Accepted Answer

Plasmids are double-stranded DNA that replicate independently and are not extracellular, while viruses can be extracellular and may have RNA or DNA genomes

Question 4

During bacterial DNA replication, which enzyme is responsible for synthesizing short RNA primers, and why are these primers necessary?

Accepted Answer

Primase; because DNA polymerases require a free 3'-OH group to extend

Question 5

Which of the following best describes the directionality of polypeptide synthesis during translation?

Accepted Answer

N-terminal to C-terminal

Question 6

A mutation in the gene encoding DNA ligase would most directly affect which step of DNA replication?

Accepted Answer

Joining of Okazaki fragments on the lagging strand

Question 7

Which of the following antibiotics inhibits bacterial translation by preventing peptide bond formation between amino acids?

Accepted Answer

Chloramphenicol

Question 8

The wobble hypothesis explains why:

Accepted Answer

A single tRNA can recognize multiple codons due to flexible base pairing at the third codon position

Question 9

Which of the following is a function of molecular chaperones in bacteria such as Escherichia coli?

Accepted Answer

They assist in the proper folding and refolding of proteins

Question 10

A bacterial gene contains a GC-rich inverted repeat followed by a central nonrepeating segment. This sequence is most likely involved in:

Accepted Answer

Rho-independent termination of transcription

Question 11

Which of the following best describes the role of the Sec system in bacterial cells?

Accepted Answer

It exports unfolded proteins and inserts integral membrane proteins

Question 12

Which of the following statements about the genetic code is correct?

Accepted Answer

There are 64 possible codons and 22 natural amino acids, making the code degenerate

Question 13

A mutation in the gene encoding aminoacyl-tRNA synthetase for lysine would most likely result in:

Accepted Answer

Inability to attach lysine to its tRNA, leading to defective protein synthesis

Question 14

Which of the following best explains why coupled transcription and translation can occur in bacteria but not in eukaryotes?

Accepted Answer

Bacteria lack a nuclear envelope, allowing ribosomes to access mRNA as it is being transcribed

Question 15

Which of the following is true regarding the structure of tRNA?

Accepted Answer

The tertiary structure is due to base pairing within the tRNA molecule

Question 16

Which of the following antibiotics blocks the attachment of tRNA to the mRNA-ribosome complex during translation?

Accepted Answer

Tetracycline

Question 17

A mutation that disrupts the signal sequence at the N-terminus of a bacterial protein would most likely affect:

Accepted Answer

The protein's secretion via the Sec or Tat system

Question 18

Which of the following best describes the function of the polyribosome (polysome) in bacterial cells?

Accepted Answer

It is a complex of several ribosomes translating a single mRNA molecule simultaneously

Question 19

Which of the following is a direct result of the degeneracy of the genetic code?

Accepted Answer

Multiple codons can encode the same amino acid

Question 20

Which of the following best describes the role of Rho protein in bacterial transcription?

Accepted Answer

It recognizes specific DNA sequences and causes termination by releasing RNA polymerase and the RNA transcript

Microbial Genetics: Molecular Information Flow and Protein Processing

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