Question 1

Which of the following best describes the structural difference between DNA and RNA?

Accepted Answer

DNA contains thymine, while RNA contains uracil.

Question 2

A prokaryotic cell is found to have a circular chromosome and several small, circular DNA molecules. What are these small DNA molecules called, and what is their primary function?

Accepted Answer

Plasmids; they often carry genes for antibiotic resistance or virulence.

Question 3

In the lac operon, which of the following events occurs when lactose is present in the environment?

Accepted Answer

The repressor is inactivated by allolactose, allowing transcription of the operon.

Question 4

Which of the following best describes a repressible operon?

Accepted Answer

It is always active unless a repressor is present.

Question 5

A mutation changes a codon from $$	ext{UAC} ($$tyrosine) to $$	ext{UAA} ($$stop codon). What type of mutation is this?

Accepted Answer

Nonsense mutation

Question 6

Which of the following is an example of a mutagen?

Accepted Answer

Ultraviolet (UV) light

Question 7

A bacterial cell exposed to UV light develops thymine dimers. Which DNA repair mechanism specifically targets these lesions?

Accepted Answer

Photoreactivation (light repair)

Question 8

In positive selection for isolating mutants, which of the following is true?

Accepted Answer

Mutants are identified by their ability to grow on selective media.

Question 9

The Ames test is used to:

Accepted Answer

Identify mutagens that may be carcinogenic.

Question 10

Which of the following best describes horizontal gene transfer?

Accepted Answer

Transfer of genetic material between unrelated organisms.

Question 11

During transformation, a bacterial cell:

Accepted Answer

Takes up naked DNA from the environment.

Question 12

In generalized transduction, which of the following occurs?

Accepted Answer

A bacteriophage transfers random fragments of bacterial DNA to another bacterium.

Question 13

Which statement about bacterial conjugation is correct?

Accepted Answer

F+ cells contain the F plasmid and can initiate conjugation.

Question 14

Transposons are best described as:

Accepted Answer

Segments of DNA that can move from one location to another within a genome.

Question 15

A frameshift mutation occurs when:

Accepted Answer

One or more nucleotides are inserted or deleted, altering the reading frame.

Question 16

Which of the following equations represents the central dogma of molecular biology?

Accepted Answer

$$	ext{DNA} ightarrow 	ext{RNA} ightarrow 	ext{Protein}$$

Question 17

A bacterial cell is exposed to a chemical that causes base-pair mismatches. Which DNA repair mechanism is most likely to correct this error?

Accepted Answer

Mismatch repair

Question 18

Which of the following is a key feature of the tryptophan operon?

Accepted Answer

It is a repressible operon inhibited by tryptophan.

Question 19

A scientist wants to determine if a chemical is a mutagen using the Ames test. Which result would indicate the chemical is a mutagen?

Accepted Answer

A significant increase in the number of revertant colonies compared to the control.

Question 20

Which of the following best describes vertical gene transfer?

Accepted Answer

Transfer of genetic material from parent to offspring during reproduction.

Microbial Genetics: Study Guide for Chapter 7

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