Selectable marker

A selectable marker is a gene introduced into a cell, especially a bacterium or to cells in culture, that confers a trait 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 other procedure meant to introduce foreign DNA into a cell. Selectable markers are often antibiotic resistance genes; bacteria that have been subjected to a procedure to introduce foreign DNA are grown on a medium containing an antibiotic, and those bacterial colonies that can grow have successfully taken up and expressed the introduced genetic material. Normally the genes encoding resistance to antibiotics such as ampicillin, chloroamphenicol, tetracycline or kanamycin, etc., are considered useful selectable markers for E.coli.

Modus operandi

The non recombinants are separated from recombinants. i.e. A r-DNA is introduced in bacteria, some bacteria are successfully transformed some remain non-transformed. When grown on medium containing ampicillin bacteria die due to lack of ampicillin resistance. The position is later noted on nitrocellulose paper and separated out to move them to nutrient medium for mass production of required product. An alternative to a selectable marker is a screenable marker, which allow the researcher to distinguish between wanted and unwanted cells, e.g. between blue and white colonies.

Positive and negative selectable markers

For molecular biology research different types of markers may be used based on the selection sought. These include:

Common selectable markers

Examples of selectable markers include:

References

  1. "positive selection". Scitable. Nature. Retrieved 29 September 2011.
  2. "negative selection". Scitable. Nature. Retrieved 29 September 2011.
  3. Callmigration.org: Gene targeting
  4. Jang, Chuan-Wei; Magnuson, Terry (20 February 2013). "A Novel Selection Marker for Efficient DNA Cloning and Recombineering in E. coli". PLoS ONE 8 (2): e57075. doi:10.1371/journal.pone.0057075. PMC 3577784. PMID 23437314.
  5. Boeke JD, LaCroute F, Fink GR (1984). "A positive selection for mutants lacking orotidine-5'-phosphate decarboxylase activity in yeast: 5-fluoro-orotic acid resistance". Mol. Gen. Genet. 197 (2): 345–6. doi:10.1007/bf00330984. PMID 6394957.


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