Bacterial Gene Expression Control Flashcards

A set of vocabulary flashcards covering bacterial gene regulation, including operon types, the Lac operon's dual control, and trp operon attenuation.

Operon

A group of related genes organized into a single regulatory unit with a common on/off switch.

Inducible operon

An operon where gene expression is usually turned off, meaning the repressor binds to the operator unless the inducer is present.

Repressible operon

An operon that is usually switched on, meaning the repressor is usually NOT bound to the operator.

Inducer

A molecule that binds to and inactivates a repressor by changing its shape, removing it from the operator and freeing the operon to be transcribed.

Co-repressor

A small molecule that binds to and activates a repressor, changing its shape to enable binding to the operator and prevent transcription.

Lac operon second switch

A regulatory mechanism sensitive to glucose concentration, ensuring the cell uses glucose before switching to lactose.

cAMP

A molecule that is high when glucose is low; it binds to CRP to allow it to promote the transcription of $LacZYA$.

CRP

A protein that binds to the promoter to promote the transcription of $LacZYA$ when it is bound to cAMP.

Attenuation

A repression system in the trp operon mediated by a leader sequence in the $5'$ end of the $trpEDCBA$ mRNA.

trpL

The $5'$ leader sequence of the trp operon that can form a hairpin structure which signals the cell to stop transcription.

Hairpin structure

A secondary structure formed by complementary sequences in the $5'$ leader sequence that looks like a transcription terminator.

tRNAtrp

The molecule whose concentration directly triggers the attenuation system in the trp operon.

Trp codons

Two adjacent sequences in the leader mRNA where translation slows down if tRNAtrp is low, preventing the formation of the hairpin terminator.