Lac and Trp Operon

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

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

• promoter
• repressor
• operator
• gene

What is the name of the stretch of DNA where RNA polymerase binds?

• operator
• promoter
• enhancer
• origin

What type of operon is the trp (tryptophan) operon?

• inducible
• repressible
• positive control
• promoible

Operons are found in the cells of which of the following types of organisms?

• prokaryotes (bacteria)
• eukaryotes (plant and animals)
• animals only
• viruses

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.

Most gene regulation happens at which step along the way?

• translation
• transcription
• signal transduction
• DNA replication

Which of the following statements regarding the trp operon is true?

• The operator region produces the mRNA that codes for the repressor.

• The regulatory gene is not transcribed in the presence of the repressor.

• Repressor proteins are inactivated by the presence of the repressor. .

• The trp operon is always activated unless deactivated by a repressor

Why is the transcription of structural genes of the trp operon turned off in the presence of tryptophan?

• Tryptophan is the repressor that binds to the operator, preventing transcription.

• The structural genes are used to make tryptophan, which would not be needed if tryptophan is available.

• Tryptophan has no effect on the transcription of the structural genes.

• Tryptophan RNA polymerase from finding the promoter of the trp operon, preventing structural gene transcription.

Tags

NGSS.HS-LS1-3