Editing Genetic transformation (section)

==History==
Transformation in bacteria was first demonstrated in 1928 by the British bacteriologist [[Frederick Griffith]].<ref name="Griffith_1928">{{cite journal | vauthors = Griffith F | title = The Significance of Pneumococcal Types | journal = The Journal of Hygiene | volume = 27 | issue = 2 | pages = 113–59 | year = 1928 | pmid = 20474956 | pmc = 2167760 | doi = 10.1017/s0022172400031879}}</ref> Griffith was interested in determining whether injections of heat-killed bacteria could be used to vaccinate mice against pneumonia.  However, he discovered that a non-virulent strain of ''[[Streptococcus pneumoniae]]'' could be made [[Virulence#Virulent bacteria|virulent]] after being exposed to heat-killed virulent strains. Griffith hypothesized that some "[[Griffith's experiment|transforming principle]]" from the heat-killed strain was responsible for making the harmless strain virulent. In 1944 this "transforming principle" was identified as being genetic by [[Oswald Avery]], [[Colin Munro MacLeod|Colin MacLeod]], and [[Maclyn McCarty]]. They isolated DNA from a virulent strain of ''S. pneumoniae'' and using just this DNA were able to make a harmless strain virulent. They called this uptake and incorporation of DNA by bacteria "transformation" (See [[Avery-MacLeod-McCarty experiment]])<ref>Case, Christine; Funke, Berdell; Tortora, Gerard. Microbiology An Introduction(tenth edition)</ref> The results of Avery et al.'s experiments were at first skeptically received by the scientific community and it was not until the development of [[genetic markers]] and the discovery of other methods of genetic transfer ([[bacterial conjugation|conjugation]] in 1947 and [[Transduction (genetics)|transduction]] in 1953) by [[Joshua Lederberg]] that Avery's experiments were accepted.<ref>{{cite journal|title = The Transformation of Genetics by DNA: An Anniversary Celebration of AVERY, MACLEOD and MCCARTY(1944) in ''Anecdotal, Historical and Critical Commentaries on Genetics'' | journal = Genetics | volume = 136 | issue = 2 | pages = 423–6 | last = Lederberg | first = Joshua| author-link = Joshua Lederberg | year= 1994 | doi = 10.1093/genetics/136.2.423 | pmid = 8150273| pmc = 1205797 }}</ref>

It was originally thought that ''[[Escherichia coli]]'', a commonly used laboratory organism, was refractory to transformation.  However, in 1970, Morton Mandel and Akiko Higa showed that ''E. coli'' may be induced to take up DNA from [[Lambda phage|bacteriophage λ]] without the use of [[Helper virus|helper phage]] after treatment with calcium chloride solution.<ref>{{cite journal | vauthors = Mandel M, Higa A | title = Calcium-dependent bacteriophage DNA infection | journal = Journal of Molecular Biology | volume = 53 | issue = 1 | pages = 159–62 | date = October 1970 | pmid = 4922220 | doi = 10.1016/0022-2836(70)90051-3 }}</ref> Two years later in 1972, [[Stanley Norman Cohen]], Annie Chang and Leslie Hsu showed that {{chem|CaCl|2}} treatment is also effective for transformation of plasmid DNA.<ref>{{cite journal | vauthors = Cohen SN, Chang AC, Hsu L | title = Nonchromosomal antibiotic resistance in bacteria: genetic transformation of Escherichia coli by R-factor DNA | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 69 | issue = 8 | pages = 2110–4 | date = August 1972 | pmid = 4559594 | pmc = 426879 | doi = 10.1073/pnas.69.8.2110 | author-link1 = Stanley Norman Cohen | bibcode = 1972PNAS...69.2110C | doi-access = free }}</ref> The method of transformation by Mandel and Higa was later improved upon by [[Douglas Hanahan]].<ref>{{cite journal | vauthors = Hanahan D | title = Studies on transformation of Escherichia coli with plasmids | journal = Journal of Molecular Biology | volume = 166 | issue = 4 | pages = 557–80 | date = June 1983 | pmid = 6345791 | doi = 10.1016/S0022-2836(83)80284-8 | citeseerx = 10.1.1.460.2021 }}</ref> The discovery of artificially induced competence in ''E. coli'' created an efficient and convenient procedure for transforming bacteria which allows for simpler [[molecular cloning]] methods in [[biotechnology]] and [[research]], and it is now a routinely used laboratory procedure.

Transformation using [[electroporation]] was developed in the late 1980s, increasing the efficiency of in-vitro transformation and increasing the number of [[bacterial strain]]s that could be transformed.<ref>{{cite journal | vauthors = Wirth R, Friesenegger A, Fiedler S | title = Transformation of various species of gram-negative bacteria belonging to 11 different genera by electroporation | journal = Molecular & General Genetics | volume = 216 | issue = 1 | pages = 175–7 | date = March 1989 | pmid = 2659971 | doi = 10.1007/BF00332248 | s2cid = 25214157 }}</ref> Transformation of animal and plant cells was also investigated with the first [[transgenic mouse]] being created by injecting a gene for a rat growth hormone into a mouse embryo in 1982.<ref>{{cite journal | vauthors = Palmiter RD, Brinster RL, Hammer RE, Trumbauer ME, Rosenfeld MG, Birnberg NC, Evans RM | title = Dramatic growth of mice that develop from eggs microinjected with metallothionein-growth hormone fusion genes | journal = Nature | volume = 300 | issue = 5893 | pages = 611–5 | date = December 1982 | pmid = 6958982 | pmc = 4881848 | doi = 10.1038/300611a0 | bibcode = 1982Natur.300..611P }}</ref> In 1897 a bacterium that caused plant tumors, ''[[Agrobacterium tumefaciens]]'', was discovered and in the early 1970s the tumor-inducing agent was found to be a DNA [[plasmid]] called the [[Ti plasmid]].<ref>{{cite web |last = Nester| first = Eugene | url = http://www.apsnet.org/publications/apsnetfeatures/Pages/Agrobacterium.aspx|title = Agrobacterium: The Natural Genetic Engineer (100 Years Later) |website = APS|publisher = The American Phytopathological Society|access-date = 14 January 2011}}</ref> By removing the genes in the plasmid that caused the tumor and adding in novel genes, researchers were able to infect plants with ''A. tumefaciens'' and let the bacteria insert their chosen DNA into the genomes of the plants.<ref>{{cite journal | vauthors = Zambryski P, Joos H, Genetello C, Leemans J, Montagu MV, Schell J | title = Ti plasmid vector for the introduction of DNA into plant cells without alteration of their normal regeneration capacity | journal = The EMBO Journal | volume = 2 | issue = 12 | pages = 2143–50 | year = 1983 | pmid = 16453482 | pmc = 555426 | doi = 10.1002/j.1460-2075.1983.tb01715.x }}</ref> Not all plant cells are susceptible to infection by ''A. tumefaciens'', so other methods were developed, including [[electroporation]] and [[Microinjection|micro-injection]].<ref>{{cite web |last = Peters| first = Pamela | url = http://www.accessexcellence.org/RC/AB/BA/Transforming_Plants.html|title = Transforming Plants - Basic Genetic Engineering Techniques|website = Access Excellence | access-date = 28 January 2010}}</ref> Particle bombardment was made possible with the invention of the [[Biolistic Particle Delivery System]] (gene gun) by [[John C. Sanford|John Sanford]] in the 1980s.<ref>{{cite news |title=Biologists invent gun for shooting cells with DNA |newspaper=Cornell Chronicle |page=3 |date=14 May 1987 |url=http://www.ecommons.cornell.edu/bitstream/1813/25239/1/018_33.pdf }}</ref><ref>{{cite journal  |vauthors=Sanford JC, Klein TM, Wolf ED, Allen N | title = Delivery of substances into cells and tissues using a particle bombardment process | journal = Journal of Particulate Science and Technology | volume = 5 | pages = 27–37 | year = 1987 | doi = 10.1080/02726358708904533 }}</ref><ref name="pmid1422046">{{cite journal | vauthors = Klein RM, Wolf ED, Wu R, Sanford JC | title = High-velocity microprojectiles for delivering nucleic acids into living cells. 1987 | journal = Biotechnology (Reading, Mass.) | volume = 24 | pages = 384–6 | year = 1992 | pmid = 1422046 }}</ref>