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A selectable marker is a gene introduced into cells, especially bacteria or cells in culture, which confers one or more traits suitable for artificial selection.They are a type of reporter gene used in laboratory microbiology, molecular biology, and genetic engineering to indicate the success of a transfection or transformation or other procedure meant to introduce foreign DNA into a cell.
In biology, a marker gene may have several meanings. In nuclear biology and molecular biology, a marker gene is a gene used to determine if a nucleic acid sequence has been successfully inserted into an organism's DNA. In particular, there are two sub-types of these marker genes: a selectable marker and a marker for screening.
Such genes are called reporters because the characteristics they confer on organisms expressing them are easily identified and measured, or because they are selectable markers. Reporter genes are often used as an indication of whether a certain gene has been taken up by or expressed in the cell or organism population.
A gene encoding a selectable marker is a common element within DNA constructs and is used to select for properly transformed cells. The selectable marker chosen will depend on the species being transformed, but it will typically be a gene granting cells a detoxification capacity for certain herbicides or antibiotics such as kanamycin ...
Trapping is performed with gene trap vectors whose principal element is a gene trapping cassette consisting of a promoterless reporter gene and/or selectable genetic marker, flanked by an upstream 3' splice site (splice acceptor; SA) and a downstream transcriptional termination sequence (polyadenylation sequence; polyA).
Since URA3 allows for both positive and negative selection, it has been developed as a genetic marker for DNA transformations and other genetic techniques in bacteria and many fungal species. It is one of the most important genetic markers in yeast genetic modification. While URA3 is a powerful selectable marker, it has a high background.
A selectable marker, which in most cases confers antibiotic resistance to the organism it is expressed in, is used to determine which cells are transformed with the new gene. The constructs are made using recombinant DNA techniques, such as restriction digests , ligations and molecular cloning .
The vectors containing the gene of interest typically also carry an antibiotic resistance gene called a selectable marker to easily identify cells that have successfully integrated the vector into their genome. To introduce a vector into a target cell, a state of competence must be inferred on the cell.