Biol 3130 Lecture 11: Control of Gene Expression

Flashcards covering key vocabulary related to gene expression control in prokaryotes (Lac Operon) and eukaryotes, including chromatin structure, histone modifications, DNA methylation, transcriptional regulation, and alternative splicing.

Lac Operon

A genetic regulatory system in prokaryotes, covered in the context of gene expression control.

lacI- mutation

A mutation in the lac regulatory gene leading to constitutive (always 'ON') transcription of the three structural genes, regardless of lactose presence.

lacI+ gene

The wild-type lac regulatory gene, which is dominant over lacI- and trans acting, enabling normal regulation of the lac operon.

trans acting

Refers to a gene product (e.g., a protein) that can diffuse from its site of synthesis to act on any copy of the DNA in the cell.

lacIS Superrepressor mutation

A mutation that makes the lac operon transcription 'OFF' continuously, meaning the repressor is always bound to the operator, even in the presence of lactose; it is dominant over lacI+ and trans acting.

CAP-cAMP complex

An activator protein complex that promotes the transcription of the lac operon structural genes in the absence of glucose and presence of lactose.

Gene Regulation in Eukaryotes vs. Prokaryotes

Eukaryotes have very few to no operons, chromatin structure impacts transcription, transcription and translation are separated by the nucleus, and they have many RNA processing and control mechanisms.

Genome

The complete set of genetic instructions for any organism, including all genes.

Transcriptome

The set of all RNA molecules transcribed in a specific cell or tissue type, specific stage of development, or under various stress conditions.

Proteome

The set of all proteins transcribed in a specific cell or tissue type.

Chromatin Structure Regulation

A major level of gene expression regulation in eukaryotes, involving chromatin remodeling, histone modifications (methylation, acetylation), and DNA methylation.

Transcriptional Regulation (Eukaryotic)

A level of gene expression regulation in eukaryotes involving different binding sites at and upstream of the promoter, transcription factors, enhancers, and silencers.

Co- and Post-transcriptional Regulation

A level of gene expression regulation in eukaryotes including mRNA processing, mRNA degradation, and RNA interference.

Translational and Post-translational Control

A level of gene expression regulation in eukaryotes involving control at the protein synthesis stage and modifications after protein synthesis.

Chromatin

The complex of chromosomal DNA and proteins within the nucleus.

Euchromatin

Chromatin that condenses and decondenses during the cell cycle, considered transcriptionally active ('open').

Heterochromatin

Chromatin that remains highly condensed throughout the cell cycle, generally considered transcriptionally inactive ('closed').

Chromatin Remodeling

A process where chromatin remodeling complexes reposition nucleosomes, allowing the transcription apparatus to bind to promoters and initiate transcription.

Histone Modification

Covalent additions of chemical groups (e.g., methyl, acetyl) to the tails of histones, which impact gene expression.

Histone Methylation

The addition of methyl (CH3) groups to histone tails by histone methyltransferases, which can activate or repress transcription.

Histone Acetylation

The addition of acetyl groups (CH3COO) to histone tails by histone acetyltransferases, typically leading to the activation of transcription by promoting open chromatin.

Histone Deacetylation

The removal of acetyl groups from histone tails by histone deacetylases (HDACs), which tends to promote condensed (closed) chromatin and repressed transcription.

DNA Methylation

The addition of methyl groups to DNA (e.g., 5-methyl-cytosine), which can make DNA inaccessible and often complexes with deacetylases to further repress transcription.

Core Promoter (Eukaryotic)

The region of a eukaryotic promoter containing several consensus sequences (e.g., TATA box at -25) where the basal transcription apparatus binds.

Regulatory Promoter (Eukaryotic)

DNA sequences located upstream from the core promoter, where transcriptional regulatory proteins bind to stimulate or inhibit transcription.

Basal Transcription Apparatus

Composed of RNA polymerase II, general transcription factors, and mediator, which binds to the core promoter to initiate transcription.

Transcriptional Activators

Proteins that bind to enhancers and regulatory promoters, stimulating the assembly and stability of the basal transcription apparatus at the core promoter and promoting transcription.

Enhancers

DNA sequences located far from the promoter that bind transcriptional activator proteins and stimulate transcription, functioning in either orientation and potentially affecting multiple genes.

Insulator

A DNA sequence that blocks the effect of an enhancer when positioned between the enhancer and the promoter, thus limiting enhancer action to specific genes.

Alternative Splicing

A regulated co-transcriptional process by which a single pre-mRNA can be spliced in different manners to generate more than one unique class of transcript and, by extension, peptide product, thus regulating gene expression.

lacOC mutation

A mutation in the Operator region of the lac operon where the repressor cannot bind, leading to constitutive expression (always 'ON') without regard to lactose.