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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.
An active enhancer regulatory sequence of DNA is enabled to interact with the promoter DNA regulatory sequence of its target gene by formation of a chromosome loop. This can initiate messenger RNA (mRNA) synthesis by RNA polymerase II (RNAP II) bound to the promoter at the transcription start site of the gene. The loop is stabilized by one ...
The cistron was defined by an operational test applicable to most organisms that is sometimes referred to as a cis-trans test, but more often as a complementation test. Richard Dawkins in his influential book The Selfish Gene argues against the cistron being the unit of selection and against it being the best definition of a gene.
In fact, many prokaryotic genes occur in operons, which are a series of genes that work together to code for the same protein or gene product and are controlled by a single promoter. [2] Bacterial RNA polymerase is made up of four subunits and when a fifth subunit attaches, called the sigma factor (σ-factor), the polymerase can recognize ...
Therefore, the rest of the operon will be transcribed and translated, so that tryptophan can be produced. Thus, domain 4 is an attenuator. Without domain 4, translation can continue regardless of the level of tryptophan. [9] The attenuator sequence has its codons translated into a leader peptide, but is not part of the trp operon gene sequence.
A structural gene is a gene that codes for any RNA or protein product other than a regulatory factor (i.e. regulatory protein).A term derived from the lac operon, structural genes are typically viewed as those containing sequences of DNA corresponding to the amino acids of a protein that will be produced, as long as said protein does not function to regulate gene expression.
Each of the individual genes in the tra operon codes for a different protein product. These products may perform a number of tasks including interaction with one another to perform mating pair functions and regulation of different regions of the tra operon itself, [6] or conjugative DNA metabolism and surface exclusion. [4]
Genealogical DNA test – used to determine ancestry or ethnic heritage for genetic genealogy. Research testing – includes finding unknown genes, learning how genes work and advancing understanding of genetic conditions. The results of testing done as part of a research study are usually not available to patients or their healthcare providers.