Question 1

Which of the following best describes a biofilm and its significance in human health?

Accepted Answer

A biofilm is a community of microorganisms attached to a surface, embedded in a matrix of polysaccharides, DNA, and proteins, which increases resistance to antimicrobial substances.

Question 2

Which of the following statements correctly differentiates between chemically defined and complex media?

Accepted Answer

Complex media contain at least one ingredient of unknown composition, such as yeast extract, while chemically defined media have all components and their concentrations known.

Question 3

A researcher is culturing an obligate anaerobe. Which of the following methods would be most appropriate to remove oxygen from the culture medium?

Accepted Answer

Adding reducing agents such as thioglycolate to the medium.

Question 4

During which phase of the bacterial growth curve is the population size static and the carrying capacity of the environment reached?

Accepted Answer

Stationary phase

Question 5

Which of the following is a direct method for measuring microbial growth?

Accepted Answer

Plate count using serial dilutions

Question 6

Which chemical agent disrupts plasma membranes and is rarely used now due to toxicity?

Accepted Answer

Phenols and phenolics

Question 7

A hospital is choosing a method to sterilize reusable surgical instruments. Which physical method is most effective for killing endospores?

Accepted Answer

Moist heat sterilization using an autoclave

Question 8

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

Accepted Answer

Sterilization removes all microorganisms including endospores, while disinfection eliminates most pathogens but not necessarily endospores.

Question 9

Which of the following statements about DNA replication in prokaryotes is correct?

Accepted Answer

DNA replication in prokaryotes is circular, so there is no end-replication problem.

Question 10

Which enzyme is responsible for unwinding the DNA double helix during replication?

Accepted Answer

Helicase

Question 11

In the process of translation, what is the role of tRNA?

Accepted Answer

tRNA brings amino acids to the ribosome where they are incorporated into proteins.

Question 12

Which of the following codons is used for the initiation of translation in prokaryotes?

Accepted Answer

$	ext{AUG}$

Question 13

Why can transcription and translation occur simultaneously in prokaryotes but not in eukaryotes?

Accepted Answer

Prokaryotes lack a nuclear membrane, allowing ribosomes to access mRNA as it is being transcribed.

Question 14

Which of the following best describes horizontal gene transfer?

Accepted Answer

Genetic information is transferred between cells of the same generation.

Question 15

A scientist uses PCR (Polymerase Chain Reaction) in a laboratory. What is the main purpose of this technique?

Accepted Answer

To amplify small samples of specific DNA sequences for further analysis.

Question 16

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

Accepted Answer

Binary fission

Question 17

Which of the following statements about mutations is correct?

Accepted Answer

Mutations are changes in the DNA sequence that can be beneficial, neutral, or harmful.

Question 18

Which of the following best describes the function of an operon in bacterial gene expression?

Accepted Answer

An operon is a group of genes regulated together, including a promoter, operator, and structural genes.

Question 19

Which of the following best explains why selective media are used in microbiology?

Accepted Answer

Selective media suppress the growth of unwanted organisms and encourage the growth of desired microbes.

Question 20

A patient is infected with a bacterium that is highly resistant to disinfectants and antiseptics. Which characteristic of the microbe is most likely responsible for this resistance?

Accepted Answer

The bacterium forms biofilms, which protect it from antimicrobial substances.

Microbial Growth, Control, and Genetics: Key Concepts and Processes

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