Selectable marker

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Selectable markers are a genes introduced into a cell, especially a bacterium or to cells in culture, that confer a 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 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, chloramphenicol, tetracycline, kanamycin, etc., are considered useful selectable markers for E. coli .

Contents

Modus operandi

The non-recombinants are separated from recombinants; that is, an r-DNA is introduced in bacteria, and some bacteria are successfully transformed while some remain non-transformed. When grown on a 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 a nutrient medium for mass production of the required product. An alternative to a selectable marker is a screenable marker, which can also be denoted as a reporter gene, which allows the researcher to distinguish between wanted and unwanted cells, such as between blue and white colonies. (see Blue–white screen) These wanted or unwanted cells are simply non-transformed cells that were unable to take up the gene during the experiment.[ citation needed ]

Positive and Negative

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

Common examples

Examples of selectable markers include:

Future developments

In the future, alternative marker technologies will need to be used more often to, at the least, assuage concerns about their persistence into the final product. It is also possible that markers will be replaced entirely by future techniques which use removable markers, and others which do not use markers at all, instead relying on co-transformation, homologous recombination, and recombinase-mediated excision. [6]

See also

Related Research Articles

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The RK2 Plasmid is a broad-host-range plasmid belonging to the incP incompatibility group It is notable for its ability to replicate in a wide variety of single-celled organisms, which makes it suitable as a genetic engineering tool. It is capable of transfer, replication, and maintenance in most genera of Gram-negative bacteria. RK2 may sometimes be referred to as pRK2, which is also the name of another, unrelated plasmid. Other names for RK2 include R18, R68, RP1, and RP4. These were all separate isolates, and later found to be identical plasmids. The IncP-1 plasmid group of which RK2 is a part has been described as "highly potent, self-transmissible, selfish DNA molecules with a complicated regulatory circuit"

Streptomyces lavendulae is a species of bacteria from the genus Streptomyces. It is isolated from soils globally and is known for its production of medically useful biologically active metabolites. To see a photo of this organism click here.

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. Bibcode:2013PLoSO...857075J. 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. S2CID   28881589.
  6. Goldstein, Daniel A.; Tinland, Bruno; Gilbertson, Lawrence A.; Staub, J.M.; Bannon, G.A.; Goodman, R.E.; McCoy, R.L.; Silvanovich, A. (2005). "Human safety and genetically modified plants: a review of antibiotic resistance markers and future transformation selection technologies". Journal of Applied Microbiology . 99 (1). Society for Applied Microbiology (Wiley): 7–23. doi:10.1111/j.1365-2672.2005.02595.x. ISSN   1364-5072. PMID   15960661. S2CID   40454719.