Biochemistry - Gene Regulation and Operons - MCAT Practice Questions

Operons are groups of genes that are regulated together and are primarily found in the DNA of which type of organism?

A. Eukaryotes
B. Prokaryotes
C. Viruses
D. Fungi

What is the binding site for RNA polymerase, the enzyme that performs transcription in an operon?

A. Operator
B. Enhancer
C. Promoter
D. Repressor

Which small molecule triggers the expression of a gene or operon by typically interacting with the repressor protein?

A. Activator
B. Corepressor
C. Inducer
D. Promoter

A repressor protein turns an operon off by binding directly to which specific region of the operon?

A. Activator site
B. Operator
C. Promoter
D. Enhancer

Under normal (default) conditions, an inducible operon is:

A. Proceeding with transcription
B. Bonded to a repressor
C. Permanently turned on
D. Permanently turned off

The lac operon is an example of which type of operon?

A. Inducible operon
B. Repressible operon
C. Constitutive operon
D. Attenuated operon

For the lac operon to be expressed (turned on), which two conditions must be met?

A. Glucose is available and Lactose is available
B. Glucose is low and Lactose is low
C. Lactose is available and Glucose is low
D. Lactose is unavailable and Glucose is high

In the lac operon, the molecule allolactose functions as the:

A. Corepressor
B. Repressor
C. Inducer
D. Activator

Which process acts to increase the accessibility of chromatin, thereby activating transcription?

A. DNA methylation
B. DNA splicing
C. Histone acetylation
D. Gene silencing

DNA methylation has what general effect on chromatin accessibility and transcription?

A. Increases accessibility; activates transcription
B. Increases accessibility; inhibits transcription
C. Decreases accessibility; inhibits transcription
D. Decreases accessibility; activates transcription

Which term refers to regions of DNA that initiate transcription and are typically located within 25 base pairs of the transcription start site?

A. Enhancers
B. Operators
C. Promoters
D. Terminators

Enhancers are sequences of DNA that function to:

A. Stop translation
B. Turn off the operon by blocking RNA polymerase
C. Enhance transcription
D. Decrease chromatin accessibility

Proteins that help turn specific genes "on" or "off" by binding to nearby DNA are collectively known as:

A. Repressors
B. Activators
C. Transcription factors
D. Corepressors

Under normal (default) conditions, a repressible operon will:

A. Be bonded to an inducer
B. Be permanently turned off
C. Proceed with transcription
D. Be bonded to a repressor

What protein binds to the DNA when glucose is low to help activate the lac operon?

A. Allolactose
B. Lac repressor
C. Catabolite Activator Protein (CAP)
D. RNA polymerase