Question 1

Which of the following best describes the function of the promoter region in a bacterial operon?

Accepted Answer

It is the site where RNA polymerase binds to initiate transcription.

Question 2

What happens when an active repressor binds to the operator region of an operon?

Accepted Answer

Transcription is prevented, and gene expression is turned off.

Question 3

In the trp operon, what role does tryptophan play in gene regulation?

Accepted Answer

It acts as a corepressor, activating the repressor and turning the operon off.

Question 4

Which of the following statements about inducible operons is correct?

Accepted Answer

They are usually off and require an inducer to inactivate the repressor and turn them on.

Question 5

What is the effect of allolactose on the lac operon?

Accepted Answer

It acts as an inducer, inactivating the repressor and allowing transcription.

Question 6

Which type of enzyme is NOT regulated and is produced at a fixed rate?

Accepted Answer

Constitutive enzyme

Question 7

During catabolite repression, what happens when both glucose and lactose are present in the growth medium for E. coli?

Accepted Answer

E. coli uses glucose first, then lactose.

Question 8

Which of the following best defines a mutation?

Accepted Answer

A change in the base sequence of DNA or genotype.

Question 9

A point mutation that results in a stop codon in the middle of mRNA is called:

Accepted Answer

Nonsense mutation

Question 10

Which of the following is true about frameshift mutations?

Accepted Answer

They cause changes in many amino acids downstream from the mutation site.

Question 11

A silent mutation is most likely to occur when:

Accepted Answer

A nucleotide is substituted at the third position of a codon.

Question 12

Which repair mechanism uses visible light to separate thymine dimers caused by UV light?

Accepted Answer

Photolyase-mediated light repair

Question 13

What is the primary function of nucleoside excision repair?

Accepted Answer

To cut out distorted cross-linked thymines and fill the gap with new DNA.

Question 14

Which of the following is a plausible outcome of a mutation?

Accepted Answer

It may be disadvantageous, lethal, or beneficial.

Question 15

Which statement best describes the relationship between repressible enzymes and anabolic pathways?

Accepted Answer

Repressible enzymes usually function in anabolic pathways and are repressed by high levels of the end product.

Question 16

If a mutation occurs in the operator region of an operon, which of the following is a likely consequence?

Accepted Answer

The repressor cannot bind, leading to continuous transcription.

Question 17

Which of the following equations best represents the process of transcription in bacteria?

Accepted Answer

$$	ext{DNA} \xrightarrow{	ext{RNA polymerase}} 	ext{mRNA}$$

Question 18

Which of the following is a common misconception about the lac operon?

Accepted Answer

The lac operon is always on regardless of environmental conditions.

Question 19

Which of the following best explains why constitutive enzymes are not regulated?

Accepted Answer

They are required for essential processes like glycolysis and must be produced continuously.

Gene Regulation and Mutation in Bacteria: Operons, Mutations, and DNA Repair

Study Guide - Practice Questions