Question 1

Which of the following best explains why DNA polymerase cannot initiate synthesis of a new DNA strand on its own during replication?

Accepted Answer

It requires a free 3'-OH group provided by an RNA primer to add nucleotides.

Question 2

A bacterial cell is exposed to both glucose and lactose. Which of the following best describes the expected transcriptional activity of the lac operon?

Accepted Answer

Transcription is minimal due to low cAMP levels and inactive CAP.

Question 3

A patient is infected with a virus that remains dormant in nerve ganglia and reactivates years later, causing a painful rash. Which viral property does this scenario illustrate?

Accepted Answer

Latency

Question 4

During the process of translation in prokaryotes, which of the following statements is correct?

Accepted Answer

Translation can begin on an mRNA molecule before transcription is complete.

Question 5

Which of the following best describes the mechanism of action for quinolone antibiotics?

Accepted Answer

They inhibit DNA gyrase, preventing relaxation of supercoiled DNA.

Question 6

A scientist is using replica plating to identify a bacterial mutant that cannot synthesize the amino acid leucine. Which type of mutant is being isolated?

Accepted Answer

Auxotroph

Question 7

Which of the following equations correctly represents the antiparallel orientation of DNA strands?

Accepted Answer

$$5' \rightarrow 3'$$ and $$3' \rightarrow 5'$$

Question 8

A bacterium acquires resistance to an antibiotic after exposure to DNA fragments from dead resistant cells in its environment. Which genetic process is responsible?

Accepted Answer

Transformation

Question 9

Which of the following best explains why viruses are not classified using binomial nomenclature?

Accepted Answer

Viruses are acellular and do not fit the criteria for genus and species classification.

Question 10

A patient develops sepsis after a local wound infection spreads via the bloodstream. Which term best describes the initial stage of this infection?

Accepted Answer

Local infection

Question 11

Which of the following is a key feature of a repressible operon such as the trp operon?

Accepted Answer

It is usually ON and is turned OFF when the end-product is abundant.

Question 12

Which of the following best describes the function of the enzyme reverse transcriptase in retroviruses?

Accepted Answer

It synthesizes double-stranded DNA from a single-stranded RNA template.

Question 13

A viral genome is described as (+) ssRNA. Which of the following statements is correct regarding its replication and translation?

Accepted Answer

The genome can be directly translated by host ribosomes as mRNA.

Question 14

Which of the following best illustrates microbial antagonism in the human body?

Accepted Answer

Lactobacilli in the vagina lower pH, inhibiting Candida albicans overgrowth.

Question 15

A hospital patient develops a urinary tract infection after catheterization. Which of the following best describes this infection?

Accepted Answer

Healthcare-associated infection (HAI)

Question 16

Which of the following best describes the role of allosteric regulation in metabolic pathways?

Accepted Answer

The end-product binds to an enzyme's allosteric site, inhibiting its activity.

Question 17

Which of the following is the correct sequence of events in the lytic cycle of a bacteriophage?

Accepted Answer

Attachment, Penetration, Biosynthesis, Maturation, Lysis

Question 18

A researcher observes that a bacterial strain can transfer chromosomal genes to a recipient via conjugation, but the recipient does not become F+. Which type of donor cell is most likely involved?

Accepted Answer

Hfr cell

Question 19

Which of the following best describes the epidemiological concept of herd immunity?

Accepted Answer

A high proportion of immune individuals in a population reduces the spread of disease.

Question 20

Which of the following is a plausible reason why antiviral drugs are more difficult to develop than antibacterial drugs?

Accepted Answer

Viruses rely on host cell machinery, so there are fewer unique viral targets for selective toxicity.

Microbial Genetics, Virology, and Epidemiology: High-Yield Study Guide

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