lecture 18: Control of Gene Expression Flashcards

Vocabulary flashcards focusing on concepts related to gene expression regulation in prokaryotes and eukaryotes from Lecture 18.

Operator

A segment of DNA usually positioned within the promoter that acts as an on-off switch for a cluster of functionally related genes.

Operon

The entire stretch of DNA that includes the operator, the promoter, and the genes that they control.

Repressor

A protein product of a separate regulatory gene that prevents gene transcription by binding to the operator and blocking RNA polymerase.

Negative Gene Regulation

A mechanism of operon regulation where genes are expressed unless they are switched off by a repressor protein.

Positive Gene Regulation

A mechanism of operon regulation where genes are expressed only when an active regulator protein, such as an activator, is present.

Corepressor

A small regulatory molecule that cooperates with a repressor protein to switch an operon off.

Repressible Operon

An operon that is switched off in response to a small regulatory molecule, such as the trp operon.

Inducible Operon

An operon that is turned on in response to a metabolite that regulates the operon, such as the lac operon.

Inducer

A molecule that inactivates the repressor protein to turn an inducible operon on.

Catabolite Activator Protein (CAP)

An activator of transcription that is activated by binding with cyclic AMP (cAMP) synthesized under low glucose conditions.

Heterochromatin

Highly packed chromatin containing genes that are usually not expressed.

Histone Acetylation

The addition of acetyl groups to histones, which masks the positive charges of amino acids.

Histone Deacetylation

The removal of acetyl groups from histones, which unmasks positive charges and leads to chromatin condensation.

Histone Methylation

The addition of methyl groups to histones, which can condense chromatin.

Histone Phosphorylation

The addition of phosphate groups next to a methylated amino acid, which can loosen chromatin.

DNA Methylation

A chemical modification to DNA associated with reduced transcription in some species.

Promoter

The binding site for transcription factors and RNA polymerase that serves as the primary site of gene expression control.

Transcription Start Site

The position at which RNA polymerase begins transcription.

Exon

Coding regions of a gene whose mRNA transcripts are spliced together to allow translation of a complete polypeptide.

Intron

Non-coding regions of a gene that are transcribed but excised during mRNA splicing.

Proximal Control Elements

Control elements that are located close to the promoter.

Distal Control Elements

Control elements, including enhancers, that may be located far away from a gene.

Activator

A protein that binds to an enhancer and stimulates transcription of a gene.

Alternative RNA Splicing

A process where different mRNA molecules are produced from the same primary transcript depending on which RNA segments are treated as exons and introns.

Ubiquitin

A molecule attached by cells to proteins to mark them for degradation.

Proteasome

A cellular structure that recognizes ubiquitin-marked proteins and degrades them.