Home > Genetically modified organism
A genetically modified organism is an organism whose genetic material has been deliberately altered. Examples are diverse, and include commercial strains of wheat that have been modified by irradiation since the 1950s, transgenic experimental animals such mice, or various microscopic organisms altered for the purposes of genetic research.1 Terminology
"Genetically modified organism" does not necessarily imply the substitution of genes from another species, although research is actively being conducted in this field. For example, genes for fluorescent proteins can be co-expressed with complex proteins in cultured cells to facilitate study by biologists, and modified organisms are of great use in researching the mechanisms of cancer and other diseases.
2 Methods of Genetic Modification
2.1 Genetic Modification of Bacteria
Three processes are known by which the genetic composition of bacteria can be altered: transformation, conjugation and transduction.
- Transformation is a process by which some bacteria are naturally capable of taking up DNA to acquire new genetic traits. This phenomenon was discovered by Frederick Griffith in 1928, although the fact that it was specifically DNA molecules that carried the genetic information was not proven until 1944Events World War II January January 4 The Battle of Monte Cassino begins. January 5 Murder of Danish playwright Kaj Munck January 17 British forces, in Italy, cross the Garigliano River. January 20 The Royal Air Force drops 2,300 tons of bombs on Berlin;. Bacteria that -- 00:38, 24 Nov 2004 (UTC)-- 00:38, 24 Nov 2004 (UTC) does not normally integrate new DNA into the bacterial chromosome2) Centromere. The point where the two chromatids touch, and where the microtubules attach. 3) Short arm. 4) Long arm. A chromosome is, minimally, a very long, continuous piece of DNA, which contains many genes, regulatory elements and other intervening n. Instead, it remains on a plasmidPlasmids are (typically) circular double stranded DNA molecules that are separate from the chromosomal DNA (Fig. They usually occur in bacteria, sometimes in eukaryotic organisms (e. the 2-micrometre-ring in Saccharomyces cerevisiae . Their size varies fr.
- In conjugation, DNA is transferred from one bacterium to another via a temporary connecting strand of DNA called a pilus (a process analogous to but biologically distinct from mating). Conjugation is not widely used for the artificial genetic modification of bacteria.
- Transduction refers to the introduction of new DNA into a bacterial cell by a bacteriophage (a virusA common alternate meaning of virus is computer virus. Other meanings, as well as a discussion of pluralization, are at plural of virus''. bacteriophage (left center); an animal virus (top right); and a retrovirus (bottom right). Viruses depend on the hos that infects bacteria).
2.2 Genetic Modification of Plants
The principal technique for the genetic modification of plantGreen algae land plants (embryophytes non-vascular embryophytes Hepatophyta liverworts Anthocerophyta hornworts Bryophyta mosses vascular plants (tracheophytes seedless vascular plants Lycopodiophyta clubmosses Equisetophyta horsetails Pteridophyta "true"s is based on a natural ability of the bacterium Agrobacterium tumefaciensAgrobacterium tumefaciens is a species of bacteria that causes tumors (commonly known as galls' or 'crown galls') on a wide range of dicots. It does so by inserting a small segment of DNA (known as the T-DNA, for 'transfer DNA') into the plant cell. The T. This bacterium infects plants and causes a tumor-like growth termed a crown gall . A. tumefaciens contains a plasmidPlasmids are (typically) circular double stranded DNA molecules that are separate from the chromosomal DNA (Fig. They usually occur in bacteria, sometimes in eukaryotic organisms (e. the 2-micrometre-ring in Saccharomyces cerevisiae . Their size varies fr (a circular piece of DNA) that transfers from the bacteria into the infected plant and integrates into the plant's genome. The transferred genes cause the plant to form the gall, which houses the bacteria and produces nutrients that support the bacteria's growth. A number of scientists contributed to this discovery throughout the late 1960s and the 1970s, with key discoveries by Jeff Schell , Marc Van Montagu , Georges Morel and Jacques Tempé . By 1983 biotechnology had reached the point where it was possible to insert additional genes of interest into A. tumefaciens and thus transfer those genes into plants.
