Question 1

Which of the following best describes the difference between induced and spontaneous mutations in microorganisms?

Accepted Answer

Induced mutations are caused by physical or chemical agents, while spontaneous mutations result from errors by DNA polymerase during DNA replication.

Question 2

A researcher exposes a bacterial culture to ultraviolet (UV) radiation. What is the most likely molecular consequence of this exposure?

Accepted Answer

Creation of pyrimidine dimers that disrupt DNA replication.

Question 3

Ethidium bromide is an example of an intercalating agent. What type of mutation does it most commonly cause?

Accepted Answer

Frameshift mutation due to insertion or deletion of base pairs

Question 4

Which of the following is a correct description of a prototroph and an auxotroph?

Accepted Answer

A prototroph is the wild-type strain that can grow on minimal media, while an auxotroph has an additional nutritional requirement for growth.

Question 5

Which of the following best explains why antibiotic resistance can spread rapidly among bacterial populations?

Accepted Answer

Antibiotic resistance genes can be transferred horizontally via plasmids and transposons.

Question 6

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

Accepted Answer

Nonsense mutation

Question 7

Which of the following mechanisms is NOT a way bacteria can resist the effects of antibiotics?

Accepted Answer

Increasing the permeability of the cell membrane to antibiotics

Question 8

The Ames test is used to detect mutagenic chemicals. Which result would indicate that a chemical is a mutagen?

Accepted Answer

More revertant colonies on the test plate compared to the control

Question 9

Which of the following statements about transposable elements is TRUE?

Accepted Answer

Autonomous transposable elements can move by themselves because they encode transposase.

Question 10

A bacterial cell acquires resistance to tetracycline via a composite transposon. Which feature is characteristic of composite transposons?

Accepted Answer

They contain IS elements at each end and move by conservative transposition.

Question 11

Which of the following best describes the 'one-gene-one-polypeptide' hypothesis?

Accepted Answer

Each gene encodes a single polypeptide, but there are exceptions such as genes for RNA molecules and alternative splicing.

Question 12

Which of the following antibiotics targets bacterial cell wall synthesis by binding to transpeptidases?

Accepted Answer

Penicillins (B-lactams)

Question 13

A mutation rate in bacteria is approximately $$10^{-6}$$ per base per generation. If a bacterial genome is $$5 	imes 10^6$ base pairs, what is the expected number of mutations per genome per generation?

Accepted Answer

$$5$$

Question 14

Which of the following is a real-world example of a selectable mutation in bacteria?

Accepted Answer

Acquisition of antibiotic resistance

Question 15

Which process allows for the transfer of free DNA from a lysed cell to a recipient bacterial cell, potentially conferring antibiotic resistance?

Accepted Answer

Transformation

Question 16

A frameshift mutation is most likely to result from which of the following events?

Accepted Answer

Insertion or deletion of one or more base pairs

Question 17

Which of the following is a mechanism by which efflux pumps contribute to antibiotic resistance?

Accepted Answer

They transport antibiotics out of the cell, lowering intracellular concentration and allowing survival at higher external concentrations.

Question 18

In the context of the stringent response, which molecule is produced in response to stalled translation and leads to dormancy in bacteria?

Accepted Answer

ppGpp (guanosine tetraphosphate and pentaphosphate)

Question 19

Which of the following statements about the emergence of antibiotic resistance is supported by historical evidence?

Accepted Answer

R plasmids encoding resistance to antibiotics existed in bacteria before humans began using those antibiotics.

Question 20

Which of the following is NOT a recommended strategy for preventing the emergence of antimicrobial drug resistance?

Accepted Answer

Increase the frequency of antibiotic use to prevent resistance.

Mutations, Mutants, and Gene Transfer: Microbial Genetics and Diversity

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