Question 1

Which of the following best describes the structure and location of the bacterial chromosome compared to a eukaryotic chromosome?

Accepted Answer

Bacterial chromosomes are circular and located in the nucleoid region, whereas eukaryotic chromosomes are linear and found within a membrane-bound nucleus.

Question 2

A scientist discovers a plasmid in a bacterial cell that carries genes for antibiotic resistance. Which type of plasmid is this, and what is its primary function?

Accepted Answer

Resistance (R) plasmid; provides resistance to antibiotics or heavy metals.

Question 3

During DNA replication in bacteria, which enzyme is responsible for joining Okazaki fragments on the lagging strand, and what is the base-pairing rule for adenine?

Accepted Answer

DNA ligase; adenine pairs with thymine ($$A \equiv T)$$

Question 4

Which statement best explains the term 'semiconservative' in DNA replication?

Accepted Answer

Each new DNA molecule consists of one parental and one newly synthesized strand.

Question 5

A mutation changes a codon from $$UAC ($$tyrosine) to $$UAA ($$stop codon). What type of mutation is this, and what is its likely effect on the protein?

Accepted Answer

Nonsense mutation; results in premature termination of translation.

Question 6

Which of the following best describes the difference between the lac operon and the trp operon in E. coli?

Accepted Answer

The lac operon is inducible and is turned on in the presence of lactose, while the trp operon is repressible and is turned off in the presence of tryptophan.

Question 7

A patient is prescribed a broad-spectrum antibiotic for a respiratory infection. After two weeks, the patient develops a severe intestinal infection caused by Clostridioides difficile. What is the most likely explanation for this outcome?

Accepted Answer

The antibiotic eliminated normal gut microbiota, reducing microbial antagonism and allowing C. difficile to proliferate.

Question 8

Which of the following is NOT a mechanism by which bacteria can acquire new genetic material through horizontal gene transfer?

Accepted Answer

Binary fission

Question 9

Which of the following best describes the action of beta-lactam antibiotics such as penicillin?

Accepted Answer

They disrupt cell wall synthesis by inhibiting transpeptidase enzymes.

Question 10

A microbiologist is using ethylene oxide to sterilize heat-sensitive medical equipment. Which of the following is a disadvantage of using ethylene oxide?

Accepted Answer

It is highly toxic and requires extensive aeration after use.

Question 11

Which of the following statements about viruses is correct?

Accepted Answer

Viruses contain either DNA or RNA as their genetic material, but never both.

Question 12

A bacteriophage infects a bacterial cell and integrates its genome into the host chromosome, remaining dormant for several generations. What is this process called, and what is the integrated viral DNA called?

Accepted Answer

Lysogenic cycle; prophage

Question 13

Which of the following best explains why antimicrobial drugs that inhibit bacterial translation do not generally affect eukaryotic cells?

Accepted Answer

Bacterial ribosomes are structurally different from eukaryotic ribosomes, allowing selective targeting.

Question 14

A laboratory technician is tasked with sterilizing a solution that cannot be heated. Which physical method would be most appropriate, and what is its mode of action?

Accepted Answer

Filtration; physically removes microbes by passing the solution through a membrane with small pores.

Question 15

Which of the following best describes the function of tRNA during translation?

Accepted Answer

tRNA carries amino acids to the ribosome and matches its anticodon to the codon on mRNA.

Question 16

A patient is infected with a virus from the family Rhabdoviridae. Based on your knowledge, what is the genome type of this virus?

Accepted Answer

Single-stranded negative-sense RNA

Question 17

Which of the following is a correct statement about prions?

Accepted Answer

Prions are infectious proteins that cause diseases by inducing misfolding of normal cellular proteins.

Question 18

A hospital is considering two chemical agents for disinfecting surfaces: hydrogen peroxide and silver nitrate. Which statement is correct regarding their uses?

Accepted Answer

Hydrogen peroxide is commonly used as a sterilant for surfaces and medical equipment, while silver nitrate is used primarily as an antiseptic for burns and eye infections.

Question 19

Which of the following best describes the difference between narrow-spectrum and broad-spectrum antimicrobial drugs?

Accepted Answer

Narrow-spectrum drugs target specific groups of microbes, reducing the risk of disrupting normal microbiota, while broad-spectrum drugs affect a wide range of microbes.

Microbial Genetics, Control, and Virology: Step-by-Step Study Guide

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