Operons review quiz

Which of the following statements about the DNA in one of your brain cells is true

• It is the same as the DNA in one of your heart cells
• most of the DNA codes for protein
• the majority of genes are likely to be transcribed
• many genes are grouped into operon-like clusters

What does the operon model attempt to explain?

• the coordinated control of gene expression in bacteria
• bacterial resistance to antibiotics
• how genes move between homologous regions of DNA
• the mechanism of viral attachment to a host cell

The tryptophan operon is a repressible operon that is

• permanently turned on.
• turned on only when tryptophan is present in the growth medium.
• turned off only when glucose is present in the growth medium.
• turned off whenever tryptophan is added to the growth medium.

For a repressible operon to be transcribed, which of the following must be true?

• A corepressor must be present.
• RNA polymerase and the active repressor must be present.
• RNA polymerase must bind to the promoter, and the repressor must be inactive.
• RNA polymerase cannot be present, and the repressor must be inactive.

What would occur if the repressor of an inducible operon were mutated so it could not bind the operator?

• Irreversible binding of the repressor to the promoter
• Buildup of a substrate for the pathway controlled by the operon
• Continuous transcription of the operon’s genes
• Reduced transcription of the operon’s genes

The "on/off" switch for an operon is called the

• promoter
• repressor
• operator
• gene

In humans (eukaryotes), proto-oncogenes can change into oncogenes that cause cancer. Which of the following best explains the presence of these potential time bombs in eukaryotic cells?

• proto-oncogenes first arose from viral infections
• proto-oncogenes normally help regulate cell division
• proto-oncogenes are mutant versions of normal genes
• cells produce proto-oncogenes as they age

The "on/off" switch for an operon is called the

• promoter
• repressor
• operator
• gene

What is an operon?

• a part of a ribsome
• a part of a Rna
• a unit made up of linked genes that code for proteins needed to do a specific task
• needed for dna replication

A protein that binds to the operator and blocks the RNA polymerase

• regulator
• repressor
• activator
• corepressor