Question 1

Which of the following statements best describes the central dogma of molecular biology?

Accepted Answer

Genetic information flows from DNA to RNA to protein.

Question 2

Which enzyme is primarily responsible for introducing negative supercoils into bacterial DNA, and what is the energy source for this process?

Accepted Answer

DNA gyrase; ATP

Question 3

A mutation in the gene encoding the sigma (σ) factor in E. coli would most directly affect which process?

Accepted Answer

The recognition of promoter sequences during transcription initiation

Question 4

Which of the following best explains why DNA replication is described as 'semiconservative'?

Accepted Answer

Each new DNA molecule consists of one parental and one newly synthesized strand.

Question 5

Which of the following is a key difference between prokaryotic and eukaryotic gene expression?

Accepted Answer

In prokaryotes, transcription and translation are coupled, while in eukaryotes they are separated by the nuclear envelope.

Question 6

Which of the following best describes the function of R plasmids in bacteria?

Accepted Answer

They confer resistance to antibiotics or other growth inhibitors.

Question 7

A bacterial cell is exposed to a new antibiotic. After several generations, some cells survive due to the presence of a plasmid. Which type of plasmid is most likely responsible for this survival?

Accepted Answer

R plasmid

Question 8

Which of the following is TRUE regarding Okazaki fragments?

Accepted Answer

They are short DNA fragments synthesized on the lagging strand.

Question 9

Which of the following best describes the role of aminoacyl-tRNA synthetase in translation?

Accepted Answer

It attaches the correct amino acid to its corresponding tRNA using ATP.

Question 10

Which of the following sequences is recognized by the primary sigma factor (σ70) in E. coli during transcription initiation?

Accepted Answer

TATAAT (Pribnow box) and TTGACA

Question 11

Which of the following is a function of the Shine–Dalgarno sequence in bacterial translation?

Accepted Answer

It aligns the mRNA on the ribosome to ensure correct start site selection.

Question 12

Which of the following best describes the process of RNA splicing in eukaryotes?

Accepted Answer

It removes introns and joins exons to form mature mRNA.

Question 13

Which of the following is NOT a function of chaperone proteins in cells?

Accepted Answer

Becoming part of the final protein structure

Question 14

Which of the following is a key feature of the Tat protein secretion system in bacteria?

Accepted Answer

It secretes folded proteins using a twin-arginine motif in the signal sequence.

Question 15

A mutation that disables the 3′→5′ exonuclease activity of DNA polymerase III would most likely result in which of the following?

Accepted Answer

Decreased accuracy of DNA replication

Question 16

Which of the following best explains why positive supercoiling is advantageous for some Archaea?

Accepted Answer

It helps prevent DNA melting at high temperatures.

Question 17

Which of the following is TRUE regarding polycistronic mRNA?

Accepted Answer

It contains multiple open reading frames, each encoding a distinct polypeptide.

Question 18

Which of the following is a correct pairing of a start codon and its corresponding amino acid in bacteria?

Accepted Answer

AUG – N-formylmethionine

Question 19

Which of the following best describes the role of the injectosome in pathogenic bacteria such as Salmonella?

Accepted Answer

It is a protein secretion system that delivers effectors directly into host cells.

Question 20

Which of the following is a function of the FtsZ protein in prokaryotic cells?

Accepted Answer

It coordinates cell division and DNA separation.

Molecular Information Flow and Protein Processing in Microorganisms

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