Prokaryotic Gene Expression

A set of vocabulary flashcards covering the principles of prokaryotic gene regulation, focusing on the lac and trp operons.

Upregulation

The process of increasing the amount of a gene expressed (mRNA) or protein to meet the specific needs of a cell.

Downregulation

The process of decreasing the levels of a gene expressed (mRNA) or protein to meet the needs of the cell.

Housekeeping genes

Genes that are expressed in all cells, such as structural proteins or enzymes required for general cellular metabolism.

Tissue-specific genes

Genes expressed in only specific cell types, such as hemoglobin in red blood cells or insulin in the pancreas.

Constitutive gene expression

The continuous expression of genes for proteins that are needed by the cell at all times, driven by transcription factors that are always active.

Inducible gene expression

Expression that occurs only when required by the cell, often in response to specific environmental signals or extracellular cues.

HOX family

A evolved family of transcription factors that are highly regulated and play a critical role during development.

Cytochrome p450 enzymes

Liver enzymes that serve as an example of how gene expression adapts to environmental changes.

Promoter Region

A region in the $5'$ area of a gene containing specific sequences recognized by transcription factors to aid in the initiation of transcription.

Coding region

The portion of a gene that contains the sequence for a product, consisting of only coding sequences in bacteria and both introns and exons in eukaryotes.

$$3' \text{ UTR}$$

The three prime untranslated region of mRNA, which is essential for mRNA stability and determines its half-life.

Operon

A package or group of specific metabolic genes located together on a chromosome that are regulated and transcribed as a single unit.

Polycistronic mRNA

An RNA transcript that codes for two or more distinct protein products.

Cis-acting elements

Regulatory DNA sequences that are part of the DNA molecule itself and are located next to the gene they regulate.

Trans-acting factors

Regulatory molecules, often proteins, that are synthesized from genes different from the gene they are targeting for regulation.

Operator

A segment of DNA within an operon that regulates transcription by serving as a binding site for a repressor protein.

Repressor

A small regulatory protein that inhibits transcription by binding to the operator and blocking RNA polymerase from initiating transcription.

Negative control

A regulatory mechanism where the binding of a protein (the repressor) to DNA inhibits gene expression.

Inducer

A molecule that binds to a repressor and changes its conformation so it can no longer bind to the operator, allowing transcription to proceed.

lac operon

A model of gene regulation in $E. coli$ used to control the metabolism of lactose when glucose is unavailable.

$\beta$-galactosidase

The protein encoded by the $lacZ$ gene that is responsible for breaking down lactose into glucose and galactose.

Permease

The protein encoded by the $lacY$ gene that allows lactose to enter the bacterial cell.

Thiogalactoside transacetylase

The enzyme encoded by the $lacA$ gene within the lac operon.

Catabolite Activator Protein (CAP)

A regulatory protein that binds to a specific site in the lac operon to maximize expression when glucose is absent.

Adenylyl cyclase

An enzyme that is inhibited by glucose; when active, it produces cAMP to facilitate positive regulation of the lac operon.

Positive regulation

Regulation that facilitates transcription, such as the binding of the cAMP-CAP complex to the CAP site to help RNA polymerase initiate transcription.

Allolactose

An isomer of lactose that acts as an inducer by binding to the lac repressor and inactivating it.

$trp$ operon

A prokaryotic operon regulated by both a repressor binding to the operator at high tryptophan levels and by transcription attenuation.