Gene Regulation in Bacteria and Eukaryotes

Operon

Gene complex with related functions and control sequences.

Operator

DNA sequence controlling transcription of operon genes.

Repressor

Protein that inhibits gene transcription by binding to operator.

Regulatory Gene

Gene encoding a protein that regulates other genes.

Corepressor

Molecule that binds to repressor, activating it.

Inducer

Molecule that inactivates a repressor, allowing transcription.

Activator

Protein that enhances transcription by binding to DNA.

Lac Operon

Inducible operon coding for lactose-digesting enzymes.

Trp Operon

Repressible operon involved in tryptophan synthesis.

Repressible Operon

Operon usually active, turned off under specific conditions.

Inducible Operon

Operon turned on by the presence of an inducer.

Differential Gene Expression

Variation in gene expression among different cell types.

Histone Acetylation

Modification that enhances gene transcription by loosening DNA.

DNA Methylation

Addition of methyl groups, typically repressing gene expression.

Epigenetic Inheritance

Transmission of gene expression patterns without DNA sequence changes.

Control Elements

DNA sequences regulating transcription by binding proteins.

Enhancers

DNA sequences that increase transcription levels when bound.

Silencers

DNA sequences that decrease transcription levels when bound.

Transcription

Process of synthesizing RNA from a DNA template.

Translation

Process of synthesizing proteins from mRNA.

Allosteric Site

Region on a protein that binds molecules, altering function.

cAMP

Cyclic AMP, a signaling molecule that activates CRP.

CRP

cAMP receptor protein that activates transcription.

Structural Gene

Gene coding for proteins, part of an operon.

Post-Transcriptional Control

Regulation of gene expression after mRNA is formed.

Constitutive Genes

Genes that are continuously expressed regardless of conditions.

Negative Control

Regulatory mechanism where repressors inhibit transcription.

Positive Control

Regulatory mechanism where activators promote transcription.

Promoter Elements

DNA sequences controlling transcription rate.

Strong Promoters

Bind RNA polymerase frequently for high transcription.

Weak Promoters

Bind RNA polymerase less frequently for low transcription.

Posttranscriptional Controls

Regulatory mechanisms after transcription occurs.

mRNA Processing

No processing occurs post-transcription in this context.

Translational Controls

Regulate the translation rate of mRNA.

Posttranslational Controls

Switches that activate or inactivate enzymes.

Feedback Inhibition

Example of posttranslational control mechanism.

Allolactose

Inducer that inactivates the lac repressor.

Transcription Activation

CRP binds DNA when cAMP is present.

Transcription Inhibition

CRP is inactive when glucose is high.

cAMP receptor protein (CRP)

Protein that activates transcription in response to cAMP.

Eukaryotic gene regulation

Includes transcriptional, posttranscriptional, translational, and posttranslational controls.

Constitutive genes

Genes that are continuously expressed.

Inducible genes

Genes activated under specific conditions.

Heat-shock proteins

Proteins produced in response to stress.

Chromosome organization

Arrangement affects gene expression in cells.

Heterochromatin

Tightly packed DNA, often inactive.

Euchromatin

Loosely packed DNA, associated with active genes.

Histone acetylation

Addition of acetyl groups, promoting transcription.

Histone methylation

Addition of methyl groups, reducing transcription.

DNA methylation

Addition of methyl groups to cytosines, blocking transcription.

Epigenetic inheritance

Inheritance of traits not involving DNA sequence changes.

Transcription factors

Proteins that regulate gene transcription.

TATA box

Promoter region essential for RNA polymerase binding.

Control elements

Noncoding DNA segments that bind transcription factors.

Activators

Proteins that stimulate transcription by binding enhancers.

Mediator proteins

Facilitate interactions between transcription factors and RNA polymerase.

Post-transcriptional control

Regulation after mRNA synthesis, including splicing.

Alternative RNA splicing

Produces different mRNA from the same primary transcript.

mRNA stability

Regulates lifespan of mRNA and protein synthesis.

Proteolytic processing

Activation of proteins by removing polypeptide segments.

Chemical modifications

Reversible changes to proteins affecting activity.

Ubiquitin

Tag for proteins targeted for degradation.

Proteasomes

Complexes that degrade ubiquitin-tagged proteins.

Proteases

Enzymes that hydrolyze peptide bonds in proteins.