Genetics Terms: Week 13

Attenuation

a proposed mechanism of control in some bacterial operons which results in premature termination of transcription

Inducer

a molecule that regulates gene expression. An inducer functions in two ways by disabling repressors. The gene is expressed because an inducer binds to the repressor.

Corepressor

a protein that cannot attach (bind) to DNA by itself, but interacts with other DNA-binding proteins to suppress the activity of certain genes.

Glucose

main sugar found in your blood. It comes from the food you eat, and is your body's main source of energy

Domain

A specific physical region or amino acid sequence in a protein which is associated with a particular function or corresponding segment of DNA.

Inducible

The production of new proteins in response to external stimuli results largely from rapid activation of gene transcription — this is known as inducible gene expression.

Operon

a cluster of genes that are transcribed together to give a single messenger RNA (mRNA) molecule, which therefore encodes multiple proteins

Positive control

the genes are expressed only when an active regulator protein, e.g. an activator, is present.

Motif

a nucleic acid sequence pattern that has some biological significance such as being DNA binding sites for a regulatory protein, i.e., a transcription factor.

Beta galactosidase

enzyme that splits lactose into glucose and galactose; it is encoded by the lacZ gene in the lac operon of the bacterium Escherichia coli.

Regulatory genes

a gene involved in controlling the expression of one or more other genes

Permease

genes play pivotal roles in root import, long-distance translocation, remobilization of organic amide-N from source organs to sinks, and other environmental stress responses.

Negative control

the genes in the operon are expressed unless they are switched off by a repressor protein.

Helix-turn-helix

a common denominator in basal and specific transcription factors from the three super-kingdoms of life.

Central dogma

genetic information flows only in one direction, from DNA, to RNA, to protein, or RNA directly to protein.

Tryptophan

essential amino acid that is either used for the synthesis of proteins, catabolised for the biosynthesis of serotonin and melatonin, or shuttled through the kynurenine pathway (KP) metabolites to produce nicotinamide adenine dinucleotide (NAD+).

Repressor protein

a protein that inhibits the expression of one or more genes.

trp 5' UTR

critical for ribosome recruitment to the mRNA and start codon choice, and plays a major role in the control of translation efficiency and shaping the cellular proteome.

Lac operon

a set of genes that are specific for uptake and metabolism of lactose and is found in E. coli and other bacteria.

Operator

a genetic sequence which allows proteins responsible for transcription to attach to the DNA sequence

Structural genes

genes that code for proteins and RNAs except regulatory factors.

Repressible

those in which the presence of a substance (a co-repressor) in the environment turns off the expression of those genes (structural genes) involved in the metabolism of that substance.

Super repressor

GalRs, have a non-inducible phenotype. Cannot be lifted by inducer

Gene regulation

the process used to control the timing, location and amount in which genes are expressed.

CAP

transcriptional activator, present as homodimer in solution, each subunit including a ligand-binding domain at the N-terminus and a DNA-binding domain at the C-terminus.

Partial diploid

A bacterium with a plasmid that carries some extra genes is known as a partial diploid.

Allolactose

a sugar molecule that can permit protein synthesis to proceed

Activator

protein (transcription factor) that increases transcription of a gene or set of genes.

Constitutive

genes are those that are always active

cAMP

a ubiquitous second messenger produced in cells in response to hormones and nutrients.

Promoter

a region of DNA upstream of a gene where relevant proteins (such as RNA polymerase and transcription factors) bind to initiate transcription of that gene.