Mar 20, 2025 Transcriptional Regulation in Prokaryotes & Eukaryotes

E. coli

A type of bacteria that can metabolize lactose sugar for energy.

lac operon

A region in the bacterial genome containing multiple genes regulated together, specifically involved in lactose metabolism.

lactose permease

A transmembrane protein coded by lacY that transports lactose into the cell.

B-galactosidase (lacZ)

An enzyme that breaks down lactose into glucose and galactose.

repressor

A protein that binds to the operator site (lacO) and prevents transcription of the lac operon when lactose is not present.

operator (lacO)

A repressor binding site that regulates the expression of the lac operon.

promoter (lacP)

The site where RNA polymerase binds to initiate transcription of the lac operon.

transcription

The process of copying a segment of DNA into RNA.

inducer

A substance that initiates gene expression; lactose acts as an inducer in the lac operon.

regulatory sequences

DNA sequences that determine the transcriptional activity of genes, recognized by transcription factor proteins.

transcription factors (TFs)

Proteins that bind to specific DNA sequences to regulate transcription.

constitutive expression

Continuous expression of a gene regardless of environmental conditions.

unrepressed state

A state in which transcription can occur because the repressor is not bound to the operator.

energy conservation

The principle by which E. coli avoids unnecessary energy expenditure by not expressing lactose metabolism genes in the absence of lactose.

glucose and galactose

The simple sugars produced from the breakdown of lactose.

galactoside

A generic term for the sugar molecules, such as glucose and galactose, formed from lactose.

laci

A gene that codes for the repressor protein in the lac operon.

lactose metabolism

The biochemical processes that enable a cell to utilize lactose as a source of energy.

activator protein

A protein that binds to a DNA sequence and increases the likelihood of transcription of a particular gene.

bioenergetics

The study of energy flow (energy transformations) within living systems.

operon function

A coordinated unit of gene regulation in bacteria, allowing for the simultaneous expression of genes that encode proteins with related functions.

gene expression

The process through which genetic information is used to produce proteins, which perform various functions in the cell.

metabolism

The set of life-sustaining chemical reactions that convert food into energy.

negative control

A regulatory mechanism where a repressor protein inhibits gene expression.

positive control

A regulatory mechanism where an activator protein enhances gene expression.

RNA polymerase

An enzyme responsible for synthesizing RNA from a DNA template during transcription.