operon, genetic regulatory system found in bacteria and their viruses in which genes coding for functionally related proteins are clustered along the DNA. This feature allows protein synthesis to be controlled coordinately in response to the needs of the cell.
An operon is a cluster of functionally-related genes that are controlled by a shared operator. Operons consist of multiple genes grouped together with a promoter and an operator. Operons are present in prokaryotes (bacteria and archaea), but are absent in eukaryotes.
- Operons are regions of DNA that are made of a group of related genes. They consist of a promoter region, an operator, and multiple related genes. - Operons are available in prokaryotes (microbes and archaea), however are missing in eukaryotes.
An operon is a cluster of genes that are transcribed together to give a single messenger RNA (mRNA) molecule, which therefore encodes multiple proteins (Fig. 16.11). Such polycistronic mRNA is typically found in prokaryotes.
An operon consists of an operator, promoter, regulator, and structural genes. The regulator gene codes for a repressor protein that binds to the operator, obstructing the promoter (thus, transcription) of the structural genes.
Based on the frequency distance distributions, we estimated a total of 630 to 700 operons in E. coli. This step opens the possibility of predicting operon organization in other bacteria whose genome sequences have been finished.
The best-studied examples of operons are from the bacterium Escherichia coli (E. coli), and they involve the enzymes of lactose metabolism and tryptophan biosynthesis. Because the lactose (lac) operon shares many features with other operons, its organization and regulation are described in detail below.
Such a cluster of genes under control of a single promoter is known as an operon. Operons are common in bacteria, but they are rare in eukaryotes such as humans.
In genetics, an operon is a functioning unit of DNA containing a cluster of genes under the control of a single promoter.
There are 3 STOP codons in the genetic code - UAG, UAA, and UGA. These codons signal the end of the polypeptide chain during translation.
A gene is the basic physical and functional unit of heredity. Genes are made up of DNA. Some genes act as instructions to make molecules called proteins. However, many genes do not code for proteins. In humans, genes vary in size from a few hundred DNA bases to more than 2 million bases.
A poly(A) tail is first added at the 3' end of each coding sequence, which results in separation from any coding sequences further downstream. A separate short RNA molecule provides a leader sequence that is trans-spliced in front of each coding sequence (except for the one at the very 5'-end of the operon).
The poly-A tail is a long chain of adenine nucleotides that is added to a messenger RNA (mRNA) molecule during RNA processing to increase the stability of the molecule. Immediately after a gene in a eukaryotic cell is transcribed, the new RNA molecule undergoes several modifications known as RNA processing.
DNA methylation regulates gene expression by recruiting proteins involved in gene repression or by inhibiting the binding of transcription factor(s) to DNA. During development, the pattern of DNA methylation in the genome changes as a result of a dynamic process involving both de novo DNA methylation and demethylation.
The promoter region is the sequence typically referred to that's right upstream or right next to where a gene is about to be transcribed. It's the region where certain regulatory elements will bind; these are proteins that will bind to help RNA get transcribed.
|Comparison||RNA Polymerase||DNA Polymerase|
|Purpose||To make RNA copies of genes||To copy the entire genome|
RNA polymerase is essential to life, and is found in all living organisms and many viruses. Depending on the organism, a RNA polymerase can be a protein complex (multi-subunit RNAP) or only consist of one subunit (single-subunit RNAP, ssRNAP), each representing an independent lineage.
A repressor is a protein that turns off the expression of one or more genes. The repressor protein works by binding to the gene's promoter region, preventing the production of messenger RNA (mRNA).