Question 1

Which of the following best describes the primary difference between prokaryotic and eukaryotic cells as observed under a light microscope?

Accepted Answer

Eukaryotic cells have a defined nucleus, whereas prokaryotic cells lack a nucleus.

Question 2

During Gram staining, why do Gram-positive bacteria retain the crystal violet stain while Gram-negative bacteria do not?

Accepted Answer

Gram-positive bacteria have a thicker peptidoglycan layer that traps the stain.

Question 3

Which of the following equations correctly represents the exponential phase of microbial growth?

Accepted Answer

$N_t = N_0 	imes 2^n$

Question 4

A patient is prescribed an antibiotic that inhibits peptidoglycan synthesis. Which type of microorganism will this drug most effectively target?

Accepted Answer

Gram-positive bacteria

Question 5

Which process involves the uptake of naked DNA fragments from the environment by a bacterial cell?

Accepted Answer

Transformation

Question 6

Which enzyme is responsible for synthesizing new DNA strands during DNA replication?

Accepted Answer

DNA polymerase

Question 7

A researcher uses agarose gel electrophoresis to analyze DNA fragments. What property of DNA allows this technique to separate fragments by size?

Accepted Answer

DNA fragments are separated based on their length, with smaller fragments moving faster through the gel.

Question 8

Which of the following best describes the function of restriction enzymes in biotechnology?

Accepted Answer

They cut DNA at specific nucleotide sequences.

Question 9

A bacterial cell is exposed to a mutagen that causes a point mutation in the lac operon. Which of the following is a possible consequence?

Accepted Answer

The cell may lose the ability to metabolize lactose.

Question 10

Which of the following best explains why viruses are not classified as living organisms?

Accepted Answer

They cannot reproduce independently outside a host cell.

Question 11

Which of the following is a correct sequence of steps in the polymerase chain reaction (PCR)?

Accepted Answer

Denaturation $\rightarrow$ Annealing $\rightarrow$ Extension

Question 12

A patient is diagnosed with a helminth infection. Which of the following best describes helminths?

Accepted Answer

Multicellular eukaryotic parasites

Question 13

Which of the following statements about innate immunity is correct?

Accepted Answer

It is the first line of defense and responds rapidly to pathogens.

Question 14

Which of the following best describes the mechanism of action of beta-lactam antibiotics?

Accepted Answer

They inhibit cell wall synthesis by targeting penicillin-binding proteins.

Question 15

A bacterial strain acquires resistance to an antibiotic via a plasmid. Which genetic process most likely facilitated this resistance?

Accepted Answer

Conjugation

Question 16

Which of the following is a key feature of adaptive immunity?

Accepted Answer

It generates memory cells for a faster response upon re-exposure.

Question 17

A patient is infected with a prion. Which of the following best describes prions?

Accepted Answer

Infectious proteins lacking nucleic acids

Question 18

Which of the following best explains why agarose gel electrophoresis is used after restriction enzyme digestion in DNA fingerprinting?

Accepted Answer

To separate DNA fragments by size for comparison

Question 19

Which of the following is a correct description of the function of the operator region in the lac operon?

Accepted Answer

It binds the repressor protein to regulate transcription.

Question 20

A bacterial culture is in stationary phase. Which of the following best explains what is occurring in the culture?

Accepted Answer

The rate of cell division equals the rate of cell death.

Microbiology Study Guide: Key Topics and Concepts

Study Guide - Practice Questions