Question 1

Which of the following best describes the process of transcription in bacterial cells?

Accepted Answer

Transcription produces mRNA from a DNA template using RNA polymerase in the cytoplasm.

Question 2

In the lac operon, which molecule acts as an inducer to initiate transcription, and what is its effect on the repressor protein?

Accepted Answer

Lactose; it binds to the repressor and inactivates it, allowing transcription.

Question 3

Which of the following best explains the difference between a repressible operon and an inducible operon?

Accepted Answer

A repressible operon is usually on and can be turned off by a co-repressor, while an inducible operon is usually off and can be turned on by an inducer.

Question 4

Which of the following mutations would most likely result in a truncated protein product?

Accepted Answer

Nonsense mutation

Question 5

A frameshift mutation occurs when:

Accepted Answer

One or more bases are inserted or deleted, altering the reading frame of the gene.

Question 6

In the Ames test, what is the primary purpose of using auxotrophic bacteria?

Accepted Answer

To determine the ability of a chemical to induce mutations that restore the ability to synthesize histidine.

Question 7

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

Accepted Answer

Transfer of genetic material between unrelated bacteria, allowing rapid acquisition of new traits.

Question 8

Which type of genetic transfer involves the uptake of naked DNA from the environment by a competent bacterial cell?

Accepted Answer

Transformation

Question 9

During bacterial conjugation, which cell type contains the F plasmid integrated into its chromosome, and what is the outcome of mating with an F- cell?

Accepted Answer

Hfr cell; the F- cell may receive chromosomal genes but usually remains F-

Question 10

Which of the following statements about plasmids is correct?

Accepted Answer

Plasmids are small, circular DNA molecules that can be transferred by conjugation, transformation, or transduction.

Question 11

What is an R factor, and why is it significant in medical microbiology?

Accepted Answer

An R factor is a plasmid that carries genes for antibiotic resistance, contributing to the spread of resistant bacteria.

Question 12

Which of the following best describes the role of a transposon in horizontal genetic transfer?

Accepted Answer

Transposons are mobile genetic elements that can move between DNA molecules, facilitating the spread of antibiotic resistance.

Question 13

According to Woese’s classification, which of the following is NOT one of the three domains?

Accepted Answer

Virus

Question 14

Which of the following is the correct way to write the scientific name of Escherichia coli?

Accepted Answer

Escherichia coli

Question 15

Which method of microbial classification relies on the analysis of ribosomal RNA sequences?

Accepted Answer

Molecular methods

Question 16

A dichotomous key is used for classification by:

Accepted Answer

Identifying organisms through a series of yes/no questions based on observable traits.

Question 17

Which of the following best explains catabolite repression in the regulation of the lac operon?

Accepted Answer

Catabolite repression occurs when glucose is present, preventing the activation of the lac operon by reducing cAMP levels.

Question 18

Which equation best represents the relationship between cAMP and catabolite activator protein (CAP) in lac operon regulation?

Accepted Answer

$$	ext{CAP} + 	ext{cAMP} ightarrow 	ext{CAP-cAMP complex}$$

Question 19

Which of the following best distinguishes a regulated gene from a constitutively expressed gene?

Accepted Answer

A regulated gene is expressed in response to environmental signals, while a constitutively expressed gene is always active.

Question 20

Which of the following methods can be used to identify microorganisms based on their protein mass spectra?

Accepted Answer

MALDI-TOF

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