*lecture 7-regulation of gene expression

Gene Expression

The process by which information in a gene is used to produce a functional protein

Differentiation

Long-term control of gene expression that causes cells with the same DNA to develop different structures and functions

Regulatory Gene

A gene that produces regulatory proteins that control the expression of other genes

Regulatory Protein

A protein that binds DNA to activate or repress transcription

Constitutive Expression

Continuous expression of essential housekeeping genes required for basic cell functions

Housekeeping Genes

Genes that are constantly expressed because they are necessary for cell survival, such as actin and GAPDH

Induction

Activation of gene expression by a signal molecule that turns an operon or regulatory protein on

Repression

Inhibition of gene expression by a signal molecule that turns an operon or regulatory protein off

Chromatin Regulation

Control of gene expression through changes in chromatin structure

Heterochromatin

Condensed chromatin that is transcriptionally inactive

Euchromatin

Relaxed chromatin that is transcriptionally active

Barr Body

An inactivated X chromosome and an example of whole-chromosome regulation

Positive Control

Gene regulation in which an active regulatory protein increases the rate of transcription

Negative Control

Gene regulation in which an active regulatory protein shuts transcription off

Regulated Gene Expression

Control of the speed or amount of protein produced from a gene

Promoter

A DNA sequence where RNA polymerase and transcription factors bind to initiate transcription

Activator Protein

A regulatory protein that binds DNA and increases transcription

Transcription Factors

Proteins that help RNA polymerase bind to DNA and begin transcription

Enhancer

A DNA control element, often far from a gene, where activators bind to increase transcription

Transcription Initiation Complex

A complex of transcription factors, activators, enhancer interactions, and RNA polymerase II required for transcription to begin

Repressor

A regulatory protein that inhibits gene expression by blocking transcription

Alternative Splicing

The process of producing different mRNA molecules from the same pre-mRNA by rearranging exons

MicroRNA (miRNA)

Small RNA molecules that bind and damage mRNA, preventing translation

Exon

An expressed region of a gene that remains in mature mRNA and codes for protein

Intron

A noncoding region removed from pre-mRNA during splicing

Ubiquitin

A small protein attached to proteins to mark them for degradation

Proteasome

A protein complex that breaks down ubiquitin-tagged proteins

Nucleosome

A structure consisting of DNA wrapped around histone proteins

Histone Acetylation

Addition of acetyl groups to histones, loosening DNA and promoting transcription

Histone Methylation

Addition of methyl groups to histones, causing DNA condensation and reducing transcription

Genomic Imprinting

A process in which methylation causes only one parental allele of a gene to be expressed

Operon

A group of functionally related genes transcribed together under the control of a single promoter and operator

Operator

A DNA sequence in an operon that acts as an on/off switch for transcription

Repressor Protein

A protein that binds the operator and blocks RNA polymerase, shutting down transcription

Corepressor

A molecule that helps a repressor remain bound to the operator

Inducer

A molecule that removes the repressor from the operator, allowing transcription

Structural Genes

Genes that code for proteins rather than regulatory molecules

Lac Operon

An inducible operon involved in lactose metabolism that is activated when lactose is present

Trp Operon

A repressible operon involved in tryptophan synthesis that is turned off when tryptophan is abundant

Positive Gene Regulation

Enhancement of transcription by regulatory proteins such as CAP-cAMP

Negative Gene Regulation

Suppression of transcription through repressors

Feedback Inhibition

A process in which the end product of a pathway inhibits further production of that product.