Question 1

Which of the following best describes the relationship between genotype and phenotype in a bacterial cell?

Accepted Answer

Genotype is the genetic makeup (DNA sequence), and phenotype is the observable traits resulting from gene expression.

Question 2

A scientist is studying a microbe that can only grow in the absence of oxygen. Which of the following best describes this organism, and how could you confirm its oxygen requirement in the lab?

Accepted Answer

It is a strict anaerobe; it will only grow at the bottom of a thioglycollate broth tube where oxygen is absent.

Question 3

Which of the following statements about DNA base pairing is correct and explains its importance in genetic information storage?

Accepted Answer

Base pairing ensures that each strand of DNA can serve as a template for accurate replication, due to specific hydrogen bonding between A-T and G-C.

Question 4

Which of the following best describes the role of RNA polymerase during gene expression?

Accepted Answer

RNA polymerase synthesizes a complementary RNA strand from a DNA template during transcription.

Question 5

A patient is diagnosed with shingles years after recovering from chickenpox. Which type of viral infection does this represent, and why?

Accepted Answer

Latent infection, because the virus remains dormant in nerve cells and can reactivate later.

Question 6

Which of the following is a key structural difference between enveloped and nonenveloped viruses?

Accepted Answer

Enveloped viruses have a lipid membrane derived from the host cell, while nonenveloped viruses do not.

Question 7

Which of the following best explains why hyperthermophiles that grow above $$100^\circ C$$ are not considered human pathogens?

Accepted Answer

The human body temperature is far below their optimal growth temperature, so they cannot grow or cause disease in humans.

Question 8

Which of the following best describes the function of ribosomes in gene expression?

Accepted Answer

Ribosomes catalyze the formation of peptide bonds between amino acids during translation.

Question 9

A food manufacturer adds high concentrations of salt to cured meats. Which microbiological principle explains why this inhibits microbial growth?

Accepted Answer

High salt increases osmotic pressure, drawing water out of microbial cells and inhibiting their growth.

Question 10

Which of the following is a property used to classify viruses taxonomically?

Accepted Answer

Type of nucleic acid (DNA or RNA), presence or absence of envelope, and capsid symmetry

Question 11

A researcher wants to culture an unknown bacterium from a soil sample. Which type of medium should they use and why?

Accepted Answer

Complex medium, because it contains a variety of nutrients that support the growth of many different bacteria, including unknowns.

Question 12

Which of the following best describes the difference between selective and differential media?

Accepted Answer

Selective media suppress unwanted microbes and encourage desired microbes; differential media allow distinguishing between different microbes based on metabolic reactions.

Question 13

Which of the following best explains why a bacterial colony does not grow to fill the entire Petri plate?

Accepted Answer

Nutrient depletion and accumulation of toxic waste products limit further growth.

Question 14

Which of the following is a key advantage for pathogens growing in biofilm communities?

Accepted Answer

Biofilms allow pathogens to evade the host immune response and resist antimicrobial agents.

Question 15

Which of the following best describes the process of binary fission in bacteria?

Accepted Answer

Bacteria reproduce by duplicating their DNA and dividing into two genetically identical daughter cells.

Question 16

During the multiplication cycle of a positive-sense ssRNA-containing animal virus, which event occurs immediately after entry and uncoating?

Accepted Answer

Biosynthesis of viral proteins and RNA using the host's machinery.

Question 17

Which of the following best explains how aerobes avoid damage by toxic forms of oxygen?

Accepted Answer

They produce enzymes such as superoxide dismutase and catalase to neutralize toxic oxygen species.

Question 18

Which of the following best distinguishes a virus from a bacterium?

Accepted Answer

Viruses lack ribosomes and cannot carry out metabolism independently, while bacteria have ribosomes and can metabolize on their own.

Question 19

Which of the following best describes the phases of microbial growth in a closed system, such as a batch culture?

Accepted Answer

Lag phase, log (exponential) phase, stationary phase, death phase

Question 20

A microbiologist is isolating bacteria from a patient sample. Why is the streak plate method necessary?

Accepted Answer

It allows for the isolation of pure colonies from a mixed population by diluting the sample across the agar surface.

Microbiology Study Guide: Genetics, Viruses, and Microbial Growth

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