![]() ![]() The transformation of genetics by DNA: an anniversary celebration of AVERY, MACLEOD and MCCARTY (1944) in Anecdotal, historical and critical commentaries on genetics. Particle bombardment was made possible with the invention of the Biolistic Particle Delivery System (gene gun) by John Sanford in 1990. tumefaciens, so other methods were developed including electroporation and micro-injection. ![]() Not all plant cells are susceptible to infection by A. tumefaciens and let the bacteria insert their chosen DNA into the genomes of the plants. By removing the genes in the plasmid which caused the tumour and adding in new genes researchers were able to infect plants with A. In 1907 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. 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. This created an efficient and convenient procedure for transforming bacteria and opened the way for biotechnology and research. Transformation did not become routine procedure in laboratories until 1972 when Cohen successfully transformed Escherichia coli by treating the bacteria with calcium chloride. Not until the discovery of other methods of genetic transfer ( conjugation in 1947 and transduction in 1953) by Joshua Lederberg were Avery's experiments accepted. The results of these experiments were at first sceptically received by the scientific community. They called this uptake and incorporation of DNA by bacteria 'transformation'. pneumoniae and using just this DNA were able to make a harmless strain virulent. They isolated DNA from a virulent strain of S. In 1944 this transforming principle was identified as being genetic by Oswald Avery, Colin MacLeod, and Maclyn McCarty. Griffith thought some " transforming principle" from the heat-killed strain was responsible for making the harmless strain virulent. Griffith discovered that a harmless strain of Streptococcus pneumoniae could be made virulent after being exposed to heat-killed virulent strains. Transformation was first demonstrated in 1928 by British bacteriologist Frederick Griffith. Introduction of foreign DNA into eukaryote cells is usually called " transfection". Transformation may also used to describe the insertion of new genetic material into nonbacterial cells, such as animal and plant cells. The other two are conjugation (transfer of genetic material between two bacterial cells in direct contact), and transduction (injection of foreign DNA by a bacteriophage into the host). ![]() Transformation is one of three processes by which outside genetic material may be brought into bacterial cells. Bacteria that are capable of being transformed, whether naturally or artificially, are called competent. Transformation occurs naturally in some species of bacteria, and can also be done artificially. In molecular biology, transformation is the genetic alteration of a cell by the direct uptake and expression of DNA from its surroundings. ![]()
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