Question 1

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

Accepted Answer

They are small, circular DNA molecules that replicate independently and often carry genes for antibiotic resistance or conjugation.

Question 2

A researcher exposes a non-virulent strain of Streptococcus pneumoniae to heat-killed virulent bacteria. The non-virulent strain becomes virulent. Which process is responsible for this change?

Accepted Answer

Transformation

Question 3

Which of the following statements correctly differentiates horizontal and vertical gene transfer?

Accepted Answer

Horizontal gene transfer involves the movement of genetic material between organisms other than by descent, while vertical gene transfer is the transmission of genetic material from parent to offspring.

Question 4

Which mechanism of horizontal gene transfer requires a virus as an intermediate to transfer DNA between bacteria?

Accepted Answer

Transduction

Question 5

A bacterial cell acquires a plasmid carrying a gene for antibiotic resistance. Which of the following best explains how this could occur?

Accepted Answer

The cell received the plasmid through conjugation via a sex pilus from a donor cell.

Question 6

Which of the following is a key role of the RecA protein in bacterial cells?

Accepted Answer

It mediates homologous recombination between donor and recipient DNA.

Question 7

Which of the following best describes a transposon?

Accepted Answer

A mobile genetic element that can move within and between DNA molecules, often carrying additional genes such as antibiotic resistance.

Question 8

During conjugation between an Hfr cell and an F- cell, which of the following outcomes is most likely?

Accepted Answer

The F- cell remains F- but may acquire new chromosomal genes from the Hfr cell.

Question 9

Which of the following is NOT a possible fate of external DNA acquired by a bacterium via horizontal gene transfer?

Accepted Answer

Immediate integration into the host genome without any recombination machinery.

Question 10

A bacterium is exposed to a chemical that inhibits the function of transposase. Which process would be most directly affected?

Accepted Answer

Movement of transposons within the genome.

Question 11

Which of the following best explains why horizontal gene transfer contributes to the rapid spread of antibiotic resistance among bacterial populations?

Accepted Answer

It enables bacteria to acquire resistance genes from unrelated species through mechanisms such as conjugation, transformation, and transduction.

Question 12

Which of the following scenarios is an example of specialized transduction?

Accepted Answer

A bacteriophage transfers only specific genes located near its integration site in the host genome to a new host.

Question 13

Which of the following is a distinguishing feature of conjugative plasmids?

Accepted Answer

They possess genes encoding the machinery for their own transfer between cells, such as the sex pilus.

Question 14

A bacterial population is exposed to a new antibiotic. After several generations, some bacteria survive due to a gene acquired from another species. Which process most likely enabled this adaptation?

Accepted Answer

Horizontal gene transfer, such as transformation, conjugation, or transduction.

Question 15

Which of the following best describes the role of homologous recombination in bacteria?

Accepted Answer

It enables the exchange of genetic material between similar DNA sequences, often mediated by RecA protein, leading to genetic diversity.

Question 16

Which of the following is a characteristic of insertion sequences (IS elements)?

Accepted Answer

They are the simplest type of transposon, containing only a transposase gene and inverted repeats.

Question 17

A scientist wants to artificially induce transformation in a bacterial culture. Which of the following treatments would most likely increase the competence of the cells?

Accepted Answer

Treating the cells with chemicals or electrical shock to alter the cell envelope.

Question 18

Which of the following equations best represents the frequency of transposition events per generation if the rate is $10^{-5}$ to $10^{-7}$ per generation?

Accepted Answer

$f = 10^{-5} 	ext{ to } 10^{-7}$

Question 19

Which of the following best explains why the E. coli O157 strain has approximately 1,500 more genes than the K12 strain?

Accepted Answer

O157 has acquired additional genes through horizontal gene transfer from other microorganisms.

Microbial Genetics: Horizontal Gene Transfer, Plasmids, Transposons, and Recombination

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