Question 1

Which of the following best describes the difference between transcription and translation in bacterial cells?

Accepted Answer

Transcription synthesizes mRNA from a DNA template in the cytoplasm, while translation synthesizes proteins from mRNA at ribosomes.

Question 2

A scientist is studying a bacterial operon that is normally OFF but can be turned ON in the presence of a specific substrate. Which type of operon is this, and what is the role of the repressor protein?

Accepted Answer

It is an inducible operon; the repressor protein is active by default and is inactivated by the inducer substrate.

Question 3

Which of the following best explains the advantage of a regulated gene over a constitutively expressed gene in bacteria?

Accepted Answer

Regulated genes allow bacteria to conserve energy by only expressing certain proteins when needed.

Question 4

In the lac operon, what is the effect of catabolite repression when glucose is present?

Accepted Answer

Catabolite repression decreases cAMP levels, preventing activation of the lac operon even if lactose is present.

Question 5

A base substitution mutation changes a codon from $$\mathrm{GAA} to$$ $$\mathrm{GAG}$$, both of which code for glutamic acid. What type of mutation is this?

Accepted Answer

Silent mutation

Question 6

Which of the following best describes the purpose of the Ames test?

Accepted Answer

To assess the mutagenic potential of chemical compounds using auxotrophic bacteria

Question 7

Which of the following is an example of horizontal genetic transfer in bacteria?

Accepted Answer

A bacterium acquiring a plasmid from another cell through conjugation

Question 8

Which of the following statements about genetic recombination in bacteria is correct?

Accepted Answer

Genetic recombination increases genetic diversity by exchanging DNA between different cells.

Question 9

A scientist observes that a bacterial cell can transfer DNA to another cell via a pilus. Which type of genetic transfer is this, and what is the likely outcome if the donor is an Hfr cell?

Accepted Answer

Conjugation; the recipient may receive chromosomal genes but rarely becomes F+.

Question 10

Which of the following best describes a plasmid and its role in genetic transfer?

Accepted Answer

A plasmid is a small circular DNA molecule 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 statements about transposons is correct?

Accepted Answer

Transposons are segments of DNA that can move within and between genomes, facilitating horizontal gene transfer.

Question 13

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

Accepted Answer

Protista

Question 14

Which of the following is the correct way to write the full scientific name of the bacterium that causes tuberculosis?

Accepted Answer

Mycobacterium tuberculosis

Question 15

A microbiologist uses a Gram stain to classify bacteria. What is being tested, and can this method be used to identify microorganisms?

Accepted Answer

Gram stain tests for cell wall structure and can help identify microorganisms.

Question 16

Which molecular method is most commonly used to compare evolutionary relationships among microorganisms by analyzing highly conserved genetic sequences?

Accepted Answer

Ribosomal RNA sequencing

Question 17

A laboratory uses MALDI-TOF to identify a bacterial isolate. What is the principle behind this method?

Accepted Answer

It analyzes the protein profile of the microorganism using mass spectrometry.

Question 18

Which of the following best differentiates a dichotomous key from a cladogram?

Accepted Answer

A dichotomous key is used for stepwise identification based on observable traits, while a cladogram shows evolutionary relationships.

Question 19

A patient is infected with a bacterial strain that has acquired resistance to multiple antibiotics. Which genetic element is most likely responsible for this, and by which mechanism could it have been acquired?

Accepted Answer

An R factor plasmid acquired by conjugation

Question 20

A frameshift mutation occurs when a single nucleotide is inserted into a gene. What is the most likely consequence for the resulting protein?

Accepted Answer

The protein will be truncated due to a premature stop codon.

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