Question 1

Which of the following best describes the structure and location of the bacterial chromosome?

Accepted Answer

It is a single, circular DNA molecule found in the nucleoid region of the cell.

Question 2

A scientist discovers a bacterium with a plasmid that encodes resistance to multiple antibiotics. Which type of plasmid is this most likely to be?

Accepted Answer

Resistance (R) plasmid

Question 3

During DNA replication in bacteria, which enzyme is responsible for joining Okazaki fragments on the lagging strand?

Accepted Answer

DNA ligase

Question 4

If a DNA strand has the sequence $$5'	ext{-}ATGCCGTA-3'$$, what is the sequence of the complementary DNA strand?

Accepted Answer

$$3'	ext{-}TACGGCAT-5'$$

Question 5

Which of the following statements about the lac operon is correct?

Accepted Answer

It is induced when lactose is present and glucose is absent.

Question 6

A point mutation that changes a codon from $$	ext{UAC} ($$tyrosine) to $$	ext{UAA} ($$stop codon) is best described as:

Accepted Answer

A nonsense mutation

Question 7

Which process involves the uptake of naked DNA from the environment by a competent bacterial cell?

Accepted Answer

Transformation

Question 8

Which of the following best describes the difference between sterilization and disinfection?

Accepted Answer

Sterilization destroys all microbes, including endospores; disinfection reduces the number of pathogenic microorganisms but may not eliminate all microbes.

Question 9

Which physical method of microbial control is most effective for sterilizing heat-sensitive medical equipment?

Accepted Answer

Ethylene oxide gas

Question 10

A hospital uses ionizing radiation to treat fresh produce in the cafeteria. What is the primary mode of action of this method?

Accepted Answer

It causes double-stranded breaks in DNA, leading to microbial death.

Question 11

Which of the following is a major advantage of semisynthetic antibiotics over natural antibiotics?

Accepted Answer

They can be modified to have a broader spectrum of activity or improved pharmacological properties.

Question 12

Which of the following best explains why Gram-negative bacteria are often more resistant to certain antimicrobial drugs?

Accepted Answer

Their outer membrane acts as a barrier to many drugs.

Question 13

A patient is prescribed both trimethoprim and sulfamethoxazole for a urinary tract infection. This is an example of:

Accepted Answer

Synergism, where the combined effect of the drugs is greater than either alone.

Question 14

Which of the following best describes the action of beta-lactam antibiotics?

Accepted Answer

They inhibit the cross-linking of peptidoglycan in bacterial cell walls.

Question 15

A laboratory test determines the minimum inhibitory concentration (MIC) of an antibiotic. What does this value represent?

Accepted Answer

The lowest concentration of the drug that prevents visible growth of a microorganism.

Question 16

Which of the following is a mechanism by which bacteria can develop resistance to antibiotics?

Accepted Answer

Producing enzymes that inactivate the drug, such as beta-lactamase.

Question 17

Which of the following statements about viruses is correct?

Accepted Answer

Viruses lack ribosomes and cannot carry out metabolism on their own.

Question 18

Which step in the lytic replication cycle of a bacteriophage is responsible for the destruction of the host cell?

Accepted Answer

Release, when the host cell is lysed to release new virions.

Question 19

Which of the following best describes a prion?

Accepted Answer

An infectious protein that can cause neurodegenerative diseases.

Question 20

A patient develops a Clostridioides difficile infection after long-term use of broad-spectrum antibiotics. This is most likely due to:

Accepted Answer

Disruption of the normal microbiota, leading to reduced microbial antagonism.

Microbial Genetics, Control, and Virology: Step-by-Step Study Guide

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