Regulation of Gene Expression Practice Flashcards

This set of vocabulary flashcards covers the mechanisms of gene expression regulation in prokaryotes and eukaryotes, including the lac operon, mutation effects, epigenetic modifications, and evolutionary examples as described in the lecture notes.

Gene expression

The process where only a subset of all the genes is functionally active in any given cell participating in a particular biological process.

Operon

A single transcription unit, common in bacteria like E. coli, where genes encoding several different proteins share the same transcriptional regulation.

Polycistronic

A single mRNA transcript, such as that produced by the lac operon, that includes multiple enzyme-coding sequences.

β-galactosidase

The enzyme encoded by the lacZ gene that digests lactose into its two constituent sugars: glucose and galactose.

Permease

The protein encoded by the lacY gene that helps to transfer lactose into the cell.

cis-elements

Short DNA sequences, such as P (promoter), O (operator), and CBS (CAP-binding site), that must be located on the same piece of DNA as the genes they regulate.

trans-regulators

Diffusible molecules, typically proteins, that bind to cis-elements to regulate transcription; they do not necessarily need to be encoded on the same piece of DNA as the genes they regulate.

Homotetramer

A protein complex formed by four identical molecules, such as the repressor encoded by the lacI gene.

Allosteric mechanism

A regulatory process where proteins, such as lacI or CAP, change their shape and functional properties after binding to a specific ligand.

CAP (cAMP binding protein)

An allostertic activator that, when bound to cAMP, binds to the CAP binding sequence (CBS) to help RNA polymerase initiate transcription.

Adenylate cyclase

The enzyme responsible for producing cAMP from ATP when glucose concentrations are low.

Constitutive mutants

Mutants that express the lac operon genes regardless of whether lactose is present in the medium.

Super-suppressor ($I^s$)

A mutant type of lacI where the repressor cannot bind lactose, causing it to constitutively repress the lac operon even when lactose is present.

Merozygotes

Partial diploids in E. coli created by using the F-factor to carry one copy of the lac operon while another exists on the genomic chromosome.

Enhancer elements

Distal eukaryotic cis-regulatory sequences where transcription factors bind to interact with RNA polymerase and increase the rate of transcription.

Silencers

Cis-regulatory elements that bind transcription factors to reduce or silence the transcription of an adjacent gene.

GAL4-UAS system

A yeast-derived genetic tool used to study gene expression consisting of a 'driver' (Gal4 transcriptional activator) and a 'responder' (UAS promoter).

Pseudogene

An inactive gene that has accumulated mutations preventing its expression, often found within gene families like the globin clusters.

Chromatin remodeling proteins

Protein complexes that regulate the compaction of chromatin by adding or removing chemical tags like methyl or acetyl groups to DNA-bound proteins.

Histone acetylation

A reversible modification generally associated with an open chromatin configuration and actively transcribed genes.

CpG sites

DNA regions where a cytosine base is followed by a guanine; these are primary targets for DNA methylation which is often associated with inactive DNA.

Epigenetics

Any heritable change in phenotype that is not associated with a change in the chromosomal DNA sequence.

Imprinting

An epigenetic phenomenon where an allele is expressed differently depending on whether it was inherited from the male or female parent, often involving DNA methylation.

Vernalization

The requirement for a plant to experience a long period of cold temperatures prior to flowering, managed by epigenetic memory.

FLC (FLOWERING LOCUS C)

A gene in Arabidopsis that encodes a transcription repressor of flowering; its expression is suppressed via histone deacetylation during winter.