Question 1

Which of the following best describes horizontal gene transfer in bacteria?

Accepted Answer

The transfer of genetic material between cells of the same generation

Question 2

Which mechanism of horizontal gene transfer involves the uptake of 'naked' DNA from the environment by a competent bacterial cell?

Accepted Answer

Transformation

Question 3

A researcher is studying a bacterial strain that can metabolize an unusual sugar not commonly found in its environment. Which genetic element is most likely responsible for this new metabolic capability?

Accepted Answer

Dissimilation plasmid

Question 4

Which of the following statements about transposons is correct?

Accepted Answer

Transposons are segments of DNA that can move from one region of DNA to another

Question 5

During conjugation, what is the role of the F (fertility) plasmid in E. coli?

Accepted Answer

It encodes for sex pili and enables transfer of the plasmid to recipient cells

Question 6

Which of the following best explains why Bacillus anthracis is considered highly virulent?

Accepted Answer

It possesses two plasmids encoding a capsule and a tripartite exotoxin

Question 7

A patient presents with severe vomiting and diarrhea after eating rice left at room temperature. Which bacterial species and toxin are most likely responsible?

Accepted Answer

Bacillus cereus, cereulide

Question 8

Which of the following is a key difference between generalized and specialized transduction?

Accepted Answer

Generalized transduction can transfer any bacterial gene, while specialized transduction transfers only specific genes near the prophage site

Question 9

Which of the following best describes the function of the protective antigen (PA) in the Bacillus anthracis exotoxin complex?

Accepted Answer

It binds to host cell receptors and facilitates entry of other toxin components

Question 10

A scientist is using electroporation to introduce a plasmid into bacterial cells. Which of the following best explains how electroporation facilitates gene transfer?

Accepted Answer

It applies a high-voltage pulse to transiently permeabilize the cell membrane, allowing DNA to enter

Question 11

Which of the following is a real-world application of Bacillus thuringiensis (Bt) toxins?

Accepted Answer

Biological insecticides and genetically modified crops expressing cry genes

Question 12

In Griffith's experiment, which result demonstrated that genetic information could be transferred between bacteria?

Accepted Answer

Mice injected with a mixture of heat-killed encapsulated and living nonencapsulated bacteria died, and encapsulated bacteria were recovered

Question 13

Which of the following best explains why horizontal gene transfer is important in bacterial evolution?

Accepted Answer

It increases genetic diversity by enabling the exchange of genes between unrelated cells

Question 14

A bacterial cell is exposed to extracellular DNA containing an antibiotic resistance gene. After uptake and recombination, the cell becomes resistant. Which process has occurred?

Accepted Answer

Transformation

Question 15

Which of the following is true regarding the specificity of DNA uptake during natural transformation in bacteria?

Accepted Answer

Some bacteria have sequence-specific uptake systems that preferentially import DNA with certain motifs

Question 16

Which of the following best describes the role of the capsule encoded by plasmid pX02 in Bacillus anthracis?

Accepted Answer

It is antiphagocytic, helping the bacterium evade the host immune system

Question 17

A strain of Bacillus cereus causes vomiting after ingestion of contaminated food. Which genetic element is directly responsible for the emetic toxin production?

Accepted Answer

Plasmid pCEREO1

Question 18

Which of the following equations best represents the probability $$P of a $$recipient cell acquiring a new gene via transformation, given the DNA uptake rate $$r$$ and the recombination efficiency $$e$$?

Accepted Answer

$$P = r 	imes e$$

Question 19

Which of the following is a key reason why genetically modified crops expressing Bt toxin are considered environmentally friendly?

Accepted Answer

Bt toxin specifically targets pest insects and has minimal effect on non-target organisms

Question 20

Which of the following best explains why the presence of gut bacteria is required for the full insecticidal activity of Bacillus thuringiensis (Bt) toxins?

Accepted Answer

Gut bacteria activate the Cry toxin by proteolytic cleavage

Horizontal Gene Transfer in Bacteria: Mechanisms and Genetic Elements

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