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A typical operon. In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter. [1] The genes are transcribed together into an mRNA strand and either translated together in the cytoplasm, or undergo splicing to create monocistronic mRNAs that are translated separately, i.e. several strands of mRNA that each encode a single gene product.
The system can also inhibit cell division and cell respiration. [1] The SOS response has been proposed as a model for bacterial evolution of certain types of antibiotic resistance. [2] The SOS response is a global response to DNA damage in which the cell cycle is arrested and DNA repair and mutagenesis are induced.
The lactose operon (lac operon) is an operon required for the transport and metabolism of lactose in E. coli and many other enteric bacteria.Although glucose is the preferred carbon source for most enteric bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available through the activity of β-galactosidase. [1]
Up-regulation is a process which occurs within a cell triggered by a signal (originating internal or external to the cell), which results in increased expression of one or more genes and as a result the proteins encoded by those genes. Conversely, down-regulation is a process resulting in decreased gene and corresponding protein expression.
The trp operon is a group of genes that are transcribed together, encoding the enzymes that produce the amino acid tryptophan in bacteria. The trp operon was first characterized in Escherichia coli , and it has since been discovered in many other bacteria. [ 1 ]
Changes in the regulation of gene networks are a common mechanism for prokaryotic evolution.An example of the effects of different regulatory environments for homologous proteins is the DNA-binding protein OmpR, which is involved in response to osmotic stress in E. coli but is involved in response to acidic environments in the close relative Salmonella Typhimurium.
Attenuators may be classified according to the type of molecule which induces the change in RNA structure. It is likely that transcription-attenuation mechanisms developed early, perhaps prior to the archaea/bacteria separation and have since evolved to use a number of different sensing molecules (the tryptophan biosynthetic operon has been found to use three different mechanisms in different ...
The gal operon is a prokaryotic operon, which encodes enzymes necessary for galactose metabolism. [1] Repression of gene expression for this operon works via binding of repressor molecules to two operators. These repressors dimerize, creating a loop in the DNA.