Question 1

Which of the following best describes the structure and location of a typical 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 small, circular DNA molecule in a bacterium that carries antibiotic resistance genes and can replicate independently of the main chromosome. What is this molecule called?

Accepted Answer

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'-ATGCCGTA-3', what is the sequence of the complementary DNA strand?

Accepted Answer

3'-TACGGCAT-5'

Question 5

Which of the following statements about the central dogma of genetics is correct?

Accepted Answer

It states that genetic information flows from DNA to RNA to protein.

Question 6

In the process of transcription in bacteria, which nucleotide is incorporated into RNA in place of thymine?

Accepted Answer

Uracil

Question 7

A mutation changes a codon from $$\mathrm{UAC} ($$tyrosine) to $$\mathrm{UAA} ($$stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 8

Which of the following best describes the function of the lac operon in E. coli?

Accepted Answer

It is induced in the presence of lactose and allows the cell to metabolize lactose.

Question 9

Which of the following is NOT a method of horizontal gene transfer in bacteria?

Accepted Answer

Binary fission

Question 10

A hospital is using a chemical to clean surgical instruments that kills all forms of microbial life, including endospores. What is this process called?

Accepted Answer

Sterilization

Question 11

Which of the following physical methods is used to preserve, rather than kill, microbes by removing water under vacuum at low temperature?

Accepted Answer

Lyophilization

Question 12

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.

Question 13

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 14

A patient is prescribed a combination of two antibiotics that work better together than either alone. What is this effect called?

Accepted Answer

Synergism

Question 15

Which of the following best describes a prion?

Accepted Answer

An infectious protein that can cause neurodegenerative diseases.

Question 16

Which of the following statements about the lytic cycle of a bacteriophage is correct?

Accepted Answer

It results in the destruction of the host cell and release of new phages.

Question 17

A virus with a single-stranded, negative-sense RNA genome must first do which of the following upon entering a host cell?

Accepted Answer

Synthesize a complementary positive-sense RNA to serve as mRNA.

Question 18

Which of the following best describes the difference between a virus in the extracellular state and the intracellular state?

Accepted Answer

Extracellular viruses are called virions and have a capsid; intracellular viruses lack the capsid.

Question 19

Which of the following antimicrobial agents is used to sterilize heat-sensitive medical equipment but is toxic and requires careful handling?

Accepted Answer

Ethylene oxide

Question 20

A patient develops a Clostridioides difficile infection after long-term use of broad-spectrum antibiotics. What is the most likely explanation for this?

Accepted Answer

The antibiotics disrupted the normal microbiota, allowing C. difficile to proliferate.

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

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