Question 1

Which of the following best describes the central dogma of genetics?

Accepted Answer

DNA is transcribed into mRNA, which is then translated into proteins.

Question 2

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

Accepted Answer

Ligase

Question 3

Which of the following statements correctly distinguishes prokaryotic from eukaryotic genetic processes?

Accepted Answer

Prokaryotes have circular chromosomes and perform transcription and translation in the cytoplasm.

Question 4

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

Accepted Answer

Silent mutation

Question 5

Which of the following best describes a plasmid?

Accepted Answer

A small, circular DNA molecule in prokaryotes that often carries non-essential but advantageous genes.

Question 6

What does it mean that DNA replication is 'semiconservative'?

Accepted Answer

Each new DNA molecule consists of one old (parental) strand and one new strand.

Question 7

Which of the following is NOT a component of a nucleotide?

Accepted Answer

A carboxyl group

Question 8

A researcher exposes bacteria to UV light, causing thymine dimers in the DNA. This is an example of:

Accepted Answer

A mutagen-induced mutation

Question 9

Which of the following best describes the function of RNA polymerase?

Accepted Answer

Synthesizes RNA from a DNA template during transcription

Question 10

Which of the following best explains why endospores are more difficult to kill than regular bacteria?

Accepted Answer

Endospores have a tough, protective outer layer that resists heat and chemicals.

Question 11

Which of the following best describes the action of alcohols as chemical antimicrobial agents?

Accepted Answer

They denature proteins and disrupt cell membranes, leading to cell death.

Question 12

Why is using a broad-spectrum antimicrobial drug potentially problematic?

Accepted Answer

It can disrupt normal microbiota, leading to secondary infections.

Question 13

Which of the following best defines 'selective toxicity' in antimicrobial therapy?

Accepted Answer

The drug targets microbial cells without harming host cells.

Question 14

A patient is infected with a bacterium that has acquired an R plasmid. What is the most likely consequence?

Accepted Answer

The bacterium will be resistant to certain antibiotics.

Question 15

Which of the following best describes the purpose of a streak plate technique in microbiology?

Accepted Answer

To isolate individual colonies from a mixed culture.

Question 16

MacConkey agar is both selective and differential. Which of the following statements is TRUE regarding its use?

Accepted Answer

It inhibits Gram-positive bacteria and differentiates lactose fermenters by color change.

Question 17

In the disk-diffusion (Kirby-Bauer) test, what does a large zone of inhibition around an antibiotic disk indicate?

Accepted Answer

The antibiotic is effective at inhibiting bacterial growth.

Question 18

Which of the following best explains why salt or sugar is used to preserve foods?

Accepted Answer

They create a hypertonic environment, causing microbial cells to lose water and become dehydrated.

Question 19

Which of the following is a correct definition of 'aseptic technique'?

Accepted Answer

A set of practices to prevent contamination of cultures and the environment.

Question 20

A scientist is testing a new chemical disinfectant. She uses both Gram-positive and Gram-negative bacteria at multiple concentrations. Why is this approach important?

Accepted Answer

Gram-positive and Gram-negative bacteria have different cell wall structures, which may affect their susceptibility to disinfectants.

Microbial Genetics, Control, and Antimicrobial Drugs: Study Guide

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