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An expression system is a system specifically designed for the production of a gene product of choice. This is normally a protein although may also be RNA, such as tRNA or a ribozyme . An expression system consists of a gene, normally encoded by DNA , and the molecular machinery required to transcribe the DNA into mRNA and translate the mRNA ...
A measurement of the amount of gene product is sometimes used to infer how active a gene is. Abnormal amounts of gene product can be correlated with disease-causing alleles, such as the overactivity of oncogenes, which can cause cancer. [1] [2] A gene is defined as "a hereditary unit of DNA that is required to produce a functional product". [3]
In the budding yeast Saccharomyces cerevisiae the number of essential genes is slightly higher, at 1000 genes (~20% of their genes). [110] Although the number is more difficult to measure in higher eukaryotes, mice and humans are estimated to have around 2000 essential genes (~10% of their genes). [111]
In biochemistry, in the biological context of organisms' regulation of gene expression and production of gene products, downregulation is the process by which a cell decreases the production and quantities of its cellular components, such as RNA and proteins, in response to an external stimulus.
Gene duplication is a major mechanism through which new genetic material is generated during molecular evolution. For example, the olfactory receptor gene family is one of the best-documented examples of pseudogenes in the human genome. More than 60 percent of the genes in this family are non-functional pseudogenes in humans.
For example, BRCA1 and BRCA2 are unrelated genes that are both named for their role in breast cancer and RPS2 and RPS3 are unrelated ribosomal proteins found in the same small subunit. The HGNC also maintains a "gene group" (formerly "gene family") classification. A gene can be a member of multiple groups, and all groups form a hierarchy.
Cis-regulatory DNA sequences that are located in DNA regions distant from the promoters of genes can have very large effects on gene expression, with some genes undergoing up to 100-fold increased expression due to such a cis-regulatory sequence. [3] These cis-regulatory sequences include enhancers, silencers, insulators and tethering elements. [4]
Gene structure is the organisation of specialised sequence elements within a gene.Genes contain most of the information necessary for living cells to survive and reproduce. [1] [2] In most organisms, genes are made of DNA, where the particular DNA sequence determines the function of the gene.