Question 1

Which of the following best describes the function of a bacterial capsule in microbial pathogenicity?

Accepted Answer

It increases virulence by allowing the microbe to evade phagocytosis by host immune cells.

Question 2

A patient develops a fever and shock after a Gram-negative bacterial infection. Which component of the bacteria is most likely responsible for these symptoms, and what is the mechanism?

Accepted Answer

Endotoxin (Lipid A of LPS); it induces cytokine release from macrophages, leading to fever and increased capillary permeability.

Question 3

Which of the following best distinguishes an epidemic disease from an endemic disease?

Accepted Answer

An epidemic disease affects a large number of people in a short time, while an endemic disease is constantly present at low levels in a specific area.

Question 4

During the polymerase chain reaction (PCR), what is the purpose of the denaturation step, and at what temperature is it typically performed?

Accepted Answer

To separate double-stranded DNA into single strands; typically at $$94^\circ\mathrm{C}.$$

Question 5

A researcher wants to express a human gene in E. coli. Why is complementary DNA (cDNA) used instead of genomic DNA?

Accepted Answer

cDNA lacks introns, which E. coli cannot process, allowing proper expression of the gene.

Question 6

Which of the following scenarios best illustrates horizontal gene transfer in bacteria?

Accepted Answer

A bacterium acquires antibiotic resistance by receiving a plasmid from another bacterium via conjugation.

Question 7

Which of the following best describes the difference between an A-B exotoxin and a superantigen?

Accepted Answer

An A-B exotoxin has separate binding and active components, while a superantigen causes excessive cytokine release by non-specifically activating T cells.

Question 8

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

Accepted Answer

Nosocomial (healthcare-associated) infection

Question 9

Which of the following statements about the lac operon in E. coli is correct?

Accepted Answer

The presence of lactose induces transcription by inactivating the repressor protein.

Question 10

Which of the following best explains why the genetic code is described as 'degenerate'?

Accepted Answer

Most amino acids are specified by more than one codon.

Question 11

A patient is infected with a bacterium that produces hyaluronidase. What is the likely effect of this enzyme on the host?

Accepted Answer

It breaks down connective tissue, facilitating the spread of the pathogen.

Question 12

Which of the following is the correct sequence of events in the stages of a disease?

Accepted Answer

Incubation period → Prodromal period → Period of illness → Period of decline → Period of convalescence

Question 13

Which laboratory technique would be most appropriate for detecting the presence of a specific DNA sequence in a sample using a labeled probe?

Accepted Answer

Southern blotting

Question 14

A mutation changes a codon from UAU (tyrosine) to UAA (stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 15

Which of the following best describes the function of restriction enzymes in recombinant DNA technology?

Accepted Answer

They cut double-stranded DNA at specific recognition sites, often producing sticky ends.

Question 16

A patient is diagnosed with bacteremia. Which of the following best describes this condition?

Accepted Answer

The presence of bacteria in the blood

Question 17

Which of the following is a real-world example of a zoonosis?

Accepted Answer

A person contracts rabies after being bitten by a dog.

Question 18

Which of the following statements about CRISPR-Cas9 is correct?

Accepted Answer

It uses a guide RNA to direct the Cas9 protein to a specific DNA sequence, where it makes a double-stranded cut.

Question 19

Which of the following best describes the role of the F plasmid in bacterial conjugation?

Accepted Answer

It contains genes for the formation of sex pili, enabling DNA transfer between bacteria.

Question 20

A patient is infected with a virus that causes the formation of syncytia in host tissues. What is the most likely consequence of this cytopathic effect?

Accepted Answer

Fusion of adjacent cells into giant, non-functional cells, disrupting normal tissue function.

Microbial Pathogenicity, Disease Principles, Biotechnology, and Microbial Genetics: Study Notes

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