AP Bio Chapter 18

What is an operon?

• A single gene controlled by multiple switches

• A cluster of functionally related genes controlled by a single "on-off switch"

• A protein complex that regulates gene expression

• A type of enzyme that interacts with DNA

Where is the operator located in an operon?

• Within the enzyme-coding genes

• Outside the promoter

• Positioned within the promoter or sometimes between the promoter and enzyme-coding genes

• At the end of the operon

What does an operon include?

• Only the promoter and the genes

• The operator and the enzyme-coding genes

• The operator, the promoter, and the genes that they control

• The repressor, the promoter, and the genes that they control

What can switch off the operon?

• A lipid molecule

• A carbohydrate molecule

• A protein repressor

• An RNA polymerase

How does the repressor prevent gene transcription?

• By accelerating RNA polymerase action

• By binding to the operator and blocking RNA polymerase

• By binding to the promoter and enhancing RNA polymerase

• By removing the operator from the DNA sequence

Where is the repressor protein produced?

• Within the operon itself

• At the operator site

• From a separate regulatory gene located some distance from the operon

• From the RNA polymerase

What can a repressor be in depending on the presence of other molecules?

• An active or inactive form

• A corepressor or an inducer

• A protein or a carbohydrate

• A DNA or RNA molecule

What is a corepressor?

• A molecule that breaks down repressor proteins

• A molecule that cooperates with a repressor protein to switch an operon off

• A molecule that activates repressor proteins

• A molecule that synthesizes amino acids

What does E. coli synthesize when it has insufficient tryptophan?

• Glucose

• Lactose

• The amino acid tryptophan

• The protein operon

What is the state of the trp operon when tryptophan levels are low?

• Repressed

• Active

• Inactive

• Induced