Question 1

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

Accepted Answer

It enables the bacterium to metabolize lactose when glucose is absent and lactose is present.

Question 2

A mutation in the DNA sequence $$5'	ext{-}ATG\,GCC\,TAA	ext{-}3'$$ changes the second codon from GCC to GTC. What is the effect on the resulting protein?

Accepted Answer

The protein will have a valine instead of an alanine at the second position.

Question 3

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

Accepted Answer

It is a repressible operon that is turned off when tryptophan is abundant.

Question 4

Which of the following best explains why UV light is effective at sterilizing surfaces?

Accepted Answer

It induces the formation of thymine dimers, which disrupt DNA replication.

Question 5

A patient is diagnosed with Creutzfeldt-Jakob Disease. Which of the following is the causative agent?

Accepted Answer

A misfolded protein known as a prion

Question 6

Which of the following best describes the difference between generalized and specialized transduction?

Accepted Answer

Generalized transduction can transfer any bacterial gene, while specialized transduction transfers only specific genes near the prophage site.

Question 7

Which of the following is a key feature of retrovirus replication, such as HIV?

Accepted Answer

The viral RNA genome is converted into DNA by reverse transcriptase.

Question 8

A laboratory is using a membrane filter to sterilize a solution. What is the minimum pore size required to effectively remove most bacteria?

Accepted Answer

$$0.22\,\mu m$$

Question 9

Which of the following best describes the mechanism of action of phenolic compounds in microbial control?

Accepted Answer

They denature proteins and disrupt cell membranes.

Question 10

A hospital is concerned about the spread of carbapenem-resistant Enterobacteriaceae (CRE). Why are these organisms particularly problematic in healthcare settings?

Accepted Answer

They are resistant to most antibiotics, making infections difficult to treat.

Question 11

Which of the following best distinguishes between PCR and RT-PCR?

Accepted Answer

RT-PCR first converts RNA to DNA using reverse transcriptase, then amplifies the DNA.

Question 12

Which of the following best describes the difference between acute, chronic, and latent viral infections?

Accepted Answer

Acute infections are rapidly cleared, chronic infections persist with ongoing virus production, and latent infections remain dormant with possible reactivation.

Question 13

Which of the following best explains why adding salt to food helps preserve it?

Accepted Answer

Salt creates a hypertonic environment, causing microbial cells to lose water and become dehydrated.

Question 14

A sample is tested for the presence of a virus using an enzyme immunoassay. What is the principle behind this technique?

Accepted Answer

It uses antibodies linked to enzymes to detect viral antigens.

Question 15

Which of the following best describes the decimal reduction time (DRT) in microbial control?

Accepted Answer

The time required to reduce a microbial population by 90% at a specific temperature.

Question 16

A researcher is using an autoclave to sterilize laboratory media. Which of the following best explains how the autoclave achieves sterilization?

Accepted Answer

By using pressurized steam at $$121^\circ C$$ for 15 minutes to denature proteins and destroy all forms of microbial life.

Question 17

Which of the following is a unique feature of prions compared to viruses?

Accepted Answer

Prions lack nucleic acids and are composed solely of protein.

Question 18

A patient is infected with a non-enveloped, double-stranded DNA virus. Which of the following is most likely to be true about this virus?

Accepted Answer

It is more resistant to desiccation and environmental stress than enveloped viruses.

Question 19

Which of the following best describes the role of the CAP-cAMP complex in the regulation of the lac operon?

Accepted Answer

It activates the lac operon by enhancing RNA polymerase binding when glucose is absent.

Question 20

A laboratory is using the disk diffusion method to test the effectiveness of several antibiotics. Which of the following best describes how this method works?

Accepted Answer

Antibiotic-impregnated disks are placed on an agar plate inoculated with bacteria, and zones of inhibition are measured.

Microbial Genetics, Viral Structure, and Control of Microbial Growth – Study Guide for Exam #2

Study Guide - Practice Questions

Study Guide - Flashcards