Question 1

Which of the following best describes a frameshift mutation and its likely effect on a protein?

Accepted Answer

A mutation that adds or removes nucleotides not in multiples of three, shifting the reading frame and potentially altering every amino acid after the mutation.

Question 2

A chemical mutagen that resembles a normal nucleotide and can be incorporated into DNA during replication is called:

Accepted Answer

Nucleoside analog

Question 3

Which of the following mutations would most likely have no effect on the resulting protein sequence?

Accepted Answer

Silent mutation

Question 4

What is the primary function of the operator region in a bacterial operon?

Accepted Answer

It is the binding site for the repressor protein, which can block transcription.

Question 5

Which of the following best explains why the lac operon is transcribed at high levels only when lactose is present and glucose is absent?

Accepted Answer

Lactose inactivates the repressor, and high cAMP (from low glucose) activates CAP, which enhances RNA polymerase binding.

Question 6

A bacterium is exposed to UV light, resulting in the formation of thymine dimers. Which enzyme can directly repair this damage using visible light?

Accepted Answer

Photolyase

Question 7

In the Ames test, what does a high number of revertant colonies (his+) indicate about the tested compound?

Accepted Answer

The compound is likely mutagenic, causing mutations that restore histidine synthesis.

Question 8

Which of the following is an example of positive selection for detecting bacterial mutants?

Accepted Answer

Identifying bacteria that grow in the presence of an antibiotic, indicating they have gained resistance.

Question 9

Which of the following statements about the trp operon is correct?

Accepted Answer

It is a repressible operon that is turned off when tryptophan acts as a corepressor.

Question 10

A frameshift mutation occurs in the gene encoding the trp repressor protein. What is the most likely outcome for the trp operon?

Accepted Answer

The operon will be constitutively expressed, and tryptophan will be synthesized even when it is abundant.

Question 11

Which of the following best describes catabolite repression in the context of the lac operon?

Accepted Answer

The presence of glucose inhibits the metabolism of lactose by lowering cAMP levels and inactivating CAP.

Question 12

Which of the following is NOT a component of a typical bacterial operon?

Accepted Answer

Ribosome binding site

Question 13

Which of the following best defines a constitutive gene?

Accepted Answer

A gene that is always expressed regardless of environmental conditions.

Question 14

Which of the following is a likely result of an intercalating agent acting on DNA during replication?

Accepted Answer

Insertion or deletion mutation leading to a frameshift

Question 15

Which of the following best describes the central dogma of molecular biology?

Accepted Answer

DNA is transcribed into RNA, which is then translated into protein.

Question 16

Which of the following is true regarding the function of an inducer in gene regulation?

Accepted Answer

An inducer binds to a repressor, inactivating it and allowing transcription to proceed.

Question 17

Which of the following best describes a missense mutation?

Accepted Answer

A mutation that changes one amino acid in the protein sequence.

Question 18

Which of the following is a real-life application of positive selection in microbiology?

Accepted Answer

Identifying bacteria that have gained antibiotic resistance by growing them on antibiotic-containing media.

Question 19

Which of the following best describes the role of cAMP in the regulation of the lac operon?

Accepted Answer

cAMP binds to CAP, activating it to enhance RNA polymerase binding to the promoter.

Bacterial Genetics: Mutations and Regulation of Gene Expression

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