BIOL 1105 Lesson 13: Control of Gene Expression

Vocabulary flashcards covering key terms and mechanisms for Lesson 13: Control of Gene Expression from BIOL 1105.

Activator

A regulatory transcription factor protein that binds to DNA to stimulate or increase the rate of transcription of a gene.

Alternate splicing

A post-transcriptional process in eukaryotes where different combinations of exons from the same pre-mRNA are spliced together, producing multiple distinct mRNA and protein variants from a single gene.

cAMP

Cyclic adenosine monophosphate; a small intracellular signaling molecule that accumulates when glucose levels are low and binds to catabolite activator protein (CAP) to activate transcription.

Chemical modification of proteins

Post-translational modifications, such as phosphorylation, methylation, or acetylation, that alter a protein's activity, stability, or cellular localization.

Chromatin remodeling complex

Large multi-protein machines that use ATP hydrolysis to alter histone-DNA interactions, repositioning nucleosomes to expose or hide DNA sequences to transcription machinery.

Coding region

The nucleotide sequence of a gene or mRNA transcript that directly encodes the amino acid sequence of a polypeptide.

DNA binding motifs

Specific structural protein domains (such as helix-turn-helix, zinc finger, or leucine zipper) that allow transcription factors to fit into the grooves of the DNA double helix and recognize specific base sequences.

Double stranded RNA

An RNA molecule composed of two complementary strands that is recognized by cellular processing enzymes to trigger RNA interference pathways.

Enhancers

DNA regulatory sequences located far upstream or downstream from a gene that bind specific transcription factors (activators) to greatly stimulate transcription.

Exons

The coding portions of a eukaryotic primary transcript that are retained and spliced together during RNA processing to form mature mRNA.

Export inhibition

A mechanism of post-transcriptional gene regulation that prevents processed mRNA molecules from exiting the nucleus through the nuclear pore complexes into the cytoplasm.

Gene

A distinct sequence of nucleotides in DNA that encodes the synthesis of a functional RNA or polypeptide product.

General transcription factors

A standard set of protein factors required at the core promoter to recruit and position RNA polymerase II for basal transcription initiation in eukaryotes.

Histones

Positively charged, basic proteins around which negatively charged DNA wraps to form structural nucleosomes.

Histone acetylation

The attachment of acetyl groups to positively charged lysine residues on histone tails, loosening chromatin structure to permit transcription factor access and gene expression.

Induction

The turning on or activation of gene expression in response to a specific signal or inducer molecule.

Initiation complex

The functional assembly of RNA polymerase and associated transcription factors bound at the promoter, ready to begin transcription.

lac operon

An inducible operon in bacteria containing genes required for the transport and metabolism of lactose, regulated by the Lac repressor and the CAP-cAMP complex.

mRNA editing

A post-transcriptional alteration of the nucleotide sequence of an mRNA transcript through chemical modification, insertion, or deletion of bases prior to translation.

miRNA

MicroRNAs; small, single-stranded non-coding RNA molecules that bind to complementary sequences on target mRNAs to block translation or cause mRNA degradation.

Negative control

A form of gene regulation where transcription is inhibited or repressed by the binding of a regulatory repressor protein to DNA.

Nucleosomes

The fundamental repeating structural units of eukaryotic chromatin, each consisting of a length of DNA coiled around a core octamer of histone proteins.

Operator

A specific DNA sequence within or adjacent to an operon's promoter that acts as a binding site for a repressor protein.

Operon

A functioning unit of genomic DNA in prokaryotes containing a cluster of genes under the control of a single shared promoter and operator.

Positive control

A form of gene regulation where transcription occurs only when or is significantly elevated when an activator protein is bound to DNA.

Post-transcriptional gene regulation

Any regulatory mechanism that modifies gene expression after mRNA has been transcribed, including RNA splicing, RNA editing, mRNA stability, and translational control.

Post-translational gene regulation

Control of gene expression that takes place after a protein is synthesized, altering its structural stability, enzymatic activity, localization, or degradation.

Primary transcript

The newly synthesized, single-stranded pre-mRNA molecule created directly from a DNA template prior to RNA processing.

Promoter

A regulatory DNA sequence upstream of a gene where RNA polymerase and transcription factors bind to initiate transcription.

Proteasome

A large, barrel-shaped cylindrical cellular protein complex that breaks down and degrades ubiquitin-tagged proteins.

Repression

The prevention or decrease of gene transcription caused by the binding of an active repressor protein.

Repressor

A regulatory protein that binds to an operator or silencer sequence to block RNA polymerase and inhibit gene transcription.

RNA polymerase

The primary enzyme responsible for synthesizing an RNA transcript by polymerizing ribonucleotides complementary to a DNA template strand.

RNA interference

A cellular mechanism (RNAi) where small non-coding RNA molecules target complementary mRNA sequences to inhibit translation or promote mRNA cleavage.

RNA splicing

The post-transcriptional process of removing non-coding introns from a pre-mRNA transcript and joining the remaining exons together.

siRNA

Small interfering RNA; short double-stranded RNA molecules that induce the degradation of mRNAs with exact complementary sequences via the RNA interference pathway.

Small RNAs

A class of non-coding RNA molecules, typically less than 30 nucleotides long (including miRNAs and siRNAs), that function in regulating gene expression post-transcriptionally.

Spliceosomes

Large complex machines composed of small nuclear ribonucleoproteins (snRNPs) that carry out the excision of introns and the ligation of exons during RNA splicing.

Specific transcription factors

Transcription factors that act as activators or repressors by binding to specific regulatory sequences (enhancers or silencers) to alter transcription in response to specific conditions or cell types.

Transcriptional gene regulation

Control mechanisms that regulate whether and how efficiently a gene is transcribed into RNA, serving as the primary control point of gene expression.

Transcription complex

The multiprotein machinery formed by RNA polymerase, general transcription factors, and mediator proteins assembled at a promoter to execute transcription.

Transcription factors

Proteins that bind to specific DNA sequences to regulate the rate of transcription of genetic information from DNA to messenger RNA.

trp operon

A repressible bacterial operon that encodes enzymes for tryptophan synthesis; it is switched off when cellular levels of tryptophan are high.

ubiquitin

A small regulatory polypeptide that attaches to target proteins to mark them for destruction by the proteasome.

ubiquitination

The enzymatic post-translational process of covalently attaching ubiquitin chains to a target protein to direct it to the proteasome for degradation.

UTR

Untranslated region; non-coding sequences of mRNA found at the 5' and 3' ends that are critical for mRNA stability, localization, and translational regulation.