Regulation of Gene Expression

Flashcards for gene expression regulation lecture notes.

Operon

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

Repressor

A protein that prevents gene transcription by binding to the operator and blocking RNA polymerase.

Corepressor

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

Repressible Operon

An operon that is usually on, but binding of a repressor to the operator shuts off transcription.

Inducible Operon

An operon that is usually off, but a molecule called an inducer inactivates the repressor and turns on transcription.

Inducer

A molecule that inactivates the repressor to turn the lac operon on (e.g., allolactose).

Inducible Enzymes

Enzymes of the lactose pathway.

Repressible Enzymes

Enzymes for tryptophan synthesis.

CAP (Catabolite Activator Protein)

An activator of transcription that is activated by binding with cyclic AMP (cAMP) when glucose is scarce.

Differential Gene Expression

The expression of different genes by cells with the same genome, leading to differences between cell types.

Heterochromatin

Highly condensed chromatin that is usually not expressed.

Histone Acetylation

The attachment of acetyl groups to positively charged lysines in histone tails, generally loosening chromatin structure and promoting the initiation of transcription.

DNA Methylation

The addition of methyl groups to certain bases in DNA, usually cytosine, which can condense chromatin and lead to reduced transcription.

Epigenetic Inheritance

The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence.

Control Elements

Segments of noncoding DNA that serve as binding sites for transcription factors that help regulate transcription.

Transcription Factors

Proteins that are essential for the transcription of all protein-coding genes. Eukaryotic RNA polymerase requires its assistance to initiate transcription.

Enhancers

Groupings of distal control elements that may be far away from a gene or even located in an intron.

Activator

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

Repressors

Transcription factors that inhibit expression of a particular gene by a variety of methods.

Alternative RNA Splicing

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

Ubiquitin

A molecule attached to a protein to mark it for destruction.

Noncoding RNAs (ncRNAs)

RNAs that regulate gene expression at several points.

MicroRNAs (miRNAs)

Small single-stranded RNA molecules that can bind to complementary mRNA sequences and degrade the mRNA or block its translation.

Small Interfering RNAs (siRNAs)

Small RNAs that cause inhibition of gene expression; this phenomenon is called RNA interference (RNAi).

Piwi-associated RNAs (piRNAs)

A class of small ncRNAs that induce formation of heterochromatin and block expression of transposons.

Nucleic Acid Hybridization

The base pairing of a strand of nucleic acid to its complementary sequence, used to detect mRNA in a cell.

In Situ Hybridization

A technique that allows us to see mRNA in place (in situ) in the intact organism.

Reverse Transcriptase–Polymerase Chain Reaction (RT-PCR)

A method for comparing the amounts of specific mRNAs in several different samples by turning sample sets of mRNAs into double-stranded DNAs with the corresponding sequences.

Complementary DNA (cDNA)

A DNA copy of an mRNA, synthesized by reverse transcriptase.

DNA Microarray Assays

Genome-wide expression studies using DNA microarrays (DNA chips) containing tiny amounts of many single-stranded DNA fragments affixed to a slide in a grid.

RNA Sequencing

An alternative to microarray analysis involving sequencing cDNA samples from different tissues or stages to discover which genes are expressed.