Question 1

Which of the following best describes the function of bacterial plasmids?

Accepted Answer

They are small, circular DNA molecules that often carry genes for antibiotic resistance and can replicate independently of the bacterial chromosome.

Question 2

During DNA replication, which enzyme is responsible for joining Okazaki fragments on the lagging strand?

Accepted Answer

DNA ligase

Question 3

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

Accepted Answer

The lac operon is only transcribed when lactose is present and glucose is absent.

Question 4

Which process is illustrated by the transfer of DNA from one bacterium to another via a sex pilus, as shown in the cartoon with two bacteria exchanging DNA?

Accepted Answer

Conjugation

Question 5

In the context of the Ames test, what does a significant increase in the number of colonies on the experimental plate indicate?

Accepted Answer

The suspected chemical is likely a mutagen, causing reverse mutations that restore histidine synthesis.

Question 6

Which of the following best explains why cDNA is used to clone eukaryotic genes in bacteria?

Accepted Answer

cDNA is synthesized from mRNA and lacks introns, which bacteria cannot process.

Question 7

Which of the following is a correct sequence of events in the classical pathway of complement activation?

Accepted Answer

Antibody binds antigen → C1 activation → C2 and C4 activation → C3 activation

Question 8

Which of the following best describes the role of opsonization in the immune response?

Accepted Answer

It coats pathogens with serum proteins, enhancing phagocytosis by immune cells.

Question 9

A patient is exposed to a pathogen for the first time. Which antibody class is produced first during the primary immune response?

Accepted Answer

IgM

Question 10

Which of the following is a key difference between innate and adaptive immunity?

Accepted Answer

Adaptive immunity has memory and improves with repeated exposure, while innate immunity does not.

Question 11

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

Accepted Answer

They cut DNA at specific sequences, generating fragments for cloning.

Question 12

Which of the following is a real-world application of DNA fingerprinting in forensic microbiology?

Accepted Answer

Tracking the source of a bioterrorism incident by matching microbial DNA from a crime scene.

Question 13

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

Accepted Answer

Multiple codons can code for the same amino acid.

Question 14

Which of the following is a correct description of the role of miRNA in gene expression?

Accepted Answer

miRNA inhibits protein synthesis by complementary base pairing with mRNA.

Question 15

A scientist wants to amplify a specific DNA sequence from a pathogen for diagnostic purposes. Which technique should they use?

Accepted Answer

Polymerase Chain Reaction (PCR)

Question 16

Which of the following is a function of IgG antibodies?

Accepted Answer

They cross the placenta to protect the fetus.

Question 17

Which of the following best describes the process of specialized transduction in bacteria?

Accepted Answer

Specific bacterial genes are packaged inside a phage and transferred to a recipient cell.

Question 18

Which of the following is a correct statement about the role of cytokines in the immune system?

Accepted Answer

Cytokines are protein messengers that regulate immune cell communication and responses.

Question 19

Which of the following best describes the outcome of complement activation known as cytolysis?

Accepted Answer

A membrane attack complex forms, creating pores in the pathogen's membrane and causing cell lysis.

Question 20

Which of the following is a correct example of artificially acquired passive immunity?

Accepted Answer

Receiving preformed antibodies by injection, such as antivenom.

Microbial Genetics and Immunity: Unit 3 Study Guide

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