Genetic engineering

Genetic engineering, also called genetic modification, is the direct manipulation of an organism's Genes may be removed, or "knocked out", using a nuclease. Gene targeting is a different technique that uses homologous recombination to change an endogenous gene, and can be used to delete a gene, remove exons, add a gene, or introduce point mutations.

An organism that is generated through genetic engineering is considered to be a Insulin-producing bacteria were commercialized in 1982 and genetically modified food has been sold since 1994. Glofish, the first GMO designed as a pet, was first sold in the United States December in 2003.^[1]

Genetic engineering techniques have been applied in numerous fields including research, agriculture, industrial biotechnology, and medicine. Enzymes used in laundry detergent and medicines such as insulin and human growth hormone are now manufactured in GM cells, experimental GM cell lines and GM animals such as mice or zebrafish are being used for research purposes, and genetically modified crops have been commercialized.

Definition

Comparison of conventional plant breeding with transgenic and cisgenic genetic modification.

Genetic engineering alters the genetic make-up of an organism using techniques that remove fused or hybridized with the host.^[4] This involves using recombinant nucleic acid (DNA or RNA) techniques to form new combinations of heritable genetic material followed by the incorporation of that material either indirectly through a vector system or directly through micro-injection, macro-injection and micro-encapsulation techniques.

Genetic engineering does not normally include traditional

Biotechnology History History of biotechnology Timeline of biotechnology Competitions and prizes in biotechnology Branches Blue Biotechnology Green Biotechnology Red Biotechnology White Biotechnology Biological Concepts Allele Artificial selection Bioreactor Cell DNA/RNA Fermentation Gene Plasmid Protein General concepts Biotechnology companies Biotechnology industrial park Biotechnology products Biotechnology law Green Revolution Human Genome Project Pharmaceutical company Basic techniques and tools Biology field Cell culture Flow cytometry Hybridoma HPLC NMR Spectroscopy Chemical field Centrifugation CSTR DSTR Crystallization Chromatography Dialysis Electrophoresis Extraction Fed Batch Filtration PFR Sedimentation Applications Animal cell culture Bioinformatics Biosynthesis Bionic architecture Cell immunity Cloning Reproductive cloning Therapeutic cloning Embryology Environmental biotechnology Genetic engineering Genetically modified organisms Molecular genetics Gene therapy Microbial biodegradation Omics Pharmacogenomics Stem cells Telomere Tissue culture Interdisciplinary fields Bioeconomy Bioengineering Biology Biopharmacology Biomedical engineering Biomedicine Biomimetics Biochemicals Biorobotics Chemical engineering Microbiology Mining Molecular biology Nanobiotechnology Virology Lists Index of biotechnology articles List of biotechnology articles List of biotechnology companies Category Portal

• GMO Safety - Information about research projects on the biological safety of genetically modified plants.
• GMO-compass, news on GMO en EU

External links

• British Medical Association (1999). The Impact of Genetic Modification on Agriculture, Food and Health. BMJ Books.  
• Donnellan, Craig (2004). Genetic Modification (Issues). Independence Educational Publishers.  
• Morgan, Sally (2003). Superfoods: Genetic Modification of Foods (Science at the Edge). Heinemann.  
• Smiley, Sophie (2005). Genetic Modification: Study Guide (Exploring the Issues). Independence Educational Publishers.  
• Watson, James D. (2007). Recombinant DNA: Genes and Genomes: A Short Course. San Francisco: W.H. Freeman.  
• Weaver, Sean; Morris, Michael (2003). "An Annotated Bibliography of Scientific Publications on the Risks Associated with Genetic Modification". Wellington, N.Z.: Victoria University 
• Zaid, A; H.G. Hughes, E. Porceddu, F. Nicholas (2001). Glossary of Biotechnology for Food and Agriculture - A Revised and Augmented Edition of the Glossary of Biotechnology and Genetic Engineering. Available in English, French, Spanish, Arabic.  

Further reading

References

See also

Critics have objected to use of genetic engineering per se on several grounds, including ethical concerns, ecological concerns, and economic concerns raised by the fact GM techniques and GM organisms are subject to intellectual property law. GMOs also are involved in controversies over GM food with respect to whether food produced from GM crops is safe, whether it should be labeled, and whether GM crops are needed to address the world's food needs. See the genetically modified food controversies article for discussion of issues about GM crops and GM food. These controversies have led to litigation, international trade disputes, and protests, and to restrictive regulation of commercial products in some countries.

Controversy

The regulation of genetic engineering concerns the approaches taken by governments to assess and manage the risks associated with the development and release of genetically modified crops. There are differences in the regulation of GM crops between countries, with some of the most marked differences occurring between the USA and Europe. Regulation varies in a given country depending on the intended use of the products of the genetic engineering. For example, a crop not intended for food use is generally not reviewed by authorities responsible for food safety.

Regulation

Genetic engineering has also been used to create novelty items such as lavender-colored [117] blue roses,^[118] and glowing fish.^[119][120]

Genetic engineering is also being used to create BioArt.^[115] Some bacteria have been genetically engineered to create black and white photographs.^[116]

BioArt and entertainment

Ethical and safety concerns have been raised around the use of genetically modified food.^[112] A major safety concern relates to the human health implications of eating genetically modified food, in particular whether toxic or allergic reactions could occur.^[113] biodiversity are important environmental issues.^[114] Ethical concerns involve religious issues, corporate control of the food supply, intellectual property rights and the level of labeling needed on genetically modified products.

The genetic engineering of agricultural crops can increase the growth rates and resistance to different diseases caused by pathogens and parasites.^[110] This is beneficial as it can greatly increase the production of food sources with the usage of fewer resources that would be required to host the world's growing populations. These modified crops would also reduce the usage of chemicals, such as fertilizers and pesticides, and therefore decrease the severity and frequency of the damages produced by these chemical pollution.^[110][111]

Another goal in generating GMOs, is to directly improve yield by accelerating growth, or making the organism more hardy (for plants, by improving salt, cold or drought tolerance).^[102] Some agriculturally important animals have been genetically modified with growth hormones to increase their size.^[109]

Another goal consists of driving the GMO to produce materials that it does not normally make. One example is "pharming", which uses crops as bioreactors to produce vaccines, drug intermediates, or drug themselves; the useful product is purified from the harvest and then used in the standard pharmaceutical production process.^[106] Cows and goats have been engineered to express drugs and other proteins in their milk, and in 2009 the FDA approved a drug produced in goat milk.^[107][108]

Another goal in generating GMOs is to modify the quality of produce by, for instance, increasing the nutritional value or providing more industrially useful qualities or quantities.^[102] The Amflora potato, for example, produces a more industrially useful blend of starches. Cows have been engineered to produce more protein in their milk to facilitate cheese production.^[103] Soybeans and canola have been genetically modified to produce more healthy oils.^[104][105]

One goal, and the first to be realized commercially, is to provide protection from environmental threats, such as cold (in the case of Ice-minus bacteria), or pathogens, such as insects or viruses, and/or resistance to herbicides. There are also fungal and virus resistant crops developed or in development.^[99][100] They have been developed to make the insect and weed management of crops easier and can indirectly increase crop yield.^[101]

One of the best-known and genetically modified fish, which are used to produce genetically modified food and materials with diverse uses. There are four main goals in generating genetically modified crops.^[98]

Bt-toxins present in peanut leaves (bottom image) protect it from extensive damage caused by European corn borer larvae (top image).^[97]

Agriculture

Bacteria have been engineered to function as sensors by expressing a fluorescent protein under certain environmental conditions.^[96]

In materials science, a genetically modified virus has been used in an academic lab as a scaffold for assembling a more environmentally friendly lithium-ion battery.^[94][95]

Experimental, lab scale industrial applications

Using genetic engineering techniques one can transform microorganisms such as bacteria or yeast, or transform cells from multicellular organisms such as insects or mammals, with a gene coding for a useful protein, such as an enzyme, so that the transformed organism will bioreactor equipment using techniques of industrial fermentation, and then purifying the protein.^[88] Some genes do not work well in bacteria, so yeast, insect cells, or mammalians cells, each a eukaryote, can also be used.^[89] These techniques are used to produce medicines such as insulin, human growth hormone, and vaccines, supplements such as tryptophan, aid in the production of food (chymosin in cheese making) and fuels.^[90] Other applications involving genetically engineered bacteria being investigated involve making the bacteria perform tasks outside their natural cycle, such as making biofuels,^[91] cleaning up oil spills, carbon and other toxic waste^[92] and detecting arsenic in drinking water.^[93]

Industrial

• Loss of function experiments, such as in a Drosophila (fruit fly), is to induce mutations in a large population and then screen the progeny for the desired mutation. A similar process can be used in both plants and prokaryotes.
• Gain of function experiments, the logical counterpart of knockouts. These are sometimes performed in conjunction with knockout experiments to more finely establish the function of the desired gene. The process is much the same as that in knockout engineering, except that the construct is designed to increase the function of the gene, usually by providing extra copies of the gene or inducing synthesis of the protein more frequently.
• Tracking experiments, which seek to gain information about the localization and interaction of the desired protein. One way to do this is to replace the wild-type gene with a 'fusion' gene, which is a juxtaposition of the wild-type gene with a reporting element such as green fluorescent protein (GFP) that will allow easy visualization of the products of the genetic modification. While this is a useful technique, the manipulation can destroy the function of the gene, creating secondary effects and possibly calling into question the results of the experiment. More sophisticated techniques are now in development that can track protein products without mitigating their function, such as the addition of small sequences that will serve as binding motifs to monoclonal antibodies.
• Expression studies aim to discover where and when specific proteins are produced. In these experiments, the DNA sequence before the DNA that codes for a protein, known as a gene's promoter bashing.

Organisms are genetically engineered to discover the functions of certain genes. This could be the effect on the phenotype of the organism, where the gene is expressed or what other genes it interacts with. These experiments generally involve loss of function, gain of function, tracking and expression.

Genetic engineering is an important tool for genetically modified bacteria in the process. Bacteria are cheap, easy to grow, clonal, multiply quickly, relatively easy to transform and can be stored at -80 °C almost indefinitely. Once a gene is isolated it can be stored inside the bacteria providing an unlimited supply for research.

Human cells in which some proteins are fused with green fluorescent protein to allow them to be visualised

Knockout mice

Research

Gene therapy is the genetic engineering of humans by replacing defective human genes with functional copies. This can occur in somatic tissue or germline tissue. If the gene is inserted into the germline tissue it can be passed down to that person's descendants.^[79][80] Gene therapy has been successfully used to treat multiple diseases, including X-linked SCID,^[81] chronic lymphocytic leukemia (CLL),^[82] and Parkinson's disease.^[83] In 2012, Glybera became the first gene therapy treatment to be approved for clinical use in either Europe or the United States after its endorsement by the European Commission.^[84][85] There are also ethical concerns should the technology be used not just for treatment, but for enhancement, modification or alteration of a human beings' appearance, adaptability, intelligence, character or behavior.^[86] The distinction between cure and enhancement can also be difficult to establish.^[87] Transhumanists consider the enhancement of humans desirable.

[78] Genetic engineering is used to create

In medicine, genetic engineering has been used to mass-produce insulin, human growth hormones, follistim (for treating infertility), human albumin, monoclonal antibodies, antihemophilic factors, vaccines and many other drugs.^[69][70] Vaccination generally involves injecting weak, live, killed or inactivated forms of viruses or their toxins into the person being immunized.^[71] Genetically engineered viruses are being developed that can still confer immunity, but lack the infectious sequences.^[72] Mouse hybridomas, cells fused together to create monoclonal antibodies, have been humanised through genetic engineering to create human monoclonal antibodies.^[73] Genetic engineering has shown promise for treating certain forms of cancer.^[74][75]

Medicine

Genetic engineering has applications in medicine, research, industry and agriculture and can be used on a wide range of plants, animals and micro organisms.

Applications

Further testing uses genome using artificially engineered nucleases, or "molecular scissors." The nucleases create specific double-stranded break (DSBs) at desired locations in the genome, and harness the cell’s endogenous mechanisms to repair the induced break by natural processes of homologous recombination (HR) and nonhomologous end-joining (NHEJ). There are currently four families of engineered nucleases: meganucleases, zinc finger nucleases (ZFNs), transcription activator-like effector nucleases (TALENs), and CRISPRs.^[67][68]

animal. homozygous for the inserted gene and must be mated together to produce a heterozygous When the offspring is produced they can be screened for the presence of the gene. All offspring from the first generation will be [66] As often only a single cell is transformed with genetic material the organism must be regenerated from that single cell. As bacteria consist of a single cell and reproduce clonally regeneration is not necessary. In plants this is accomplished through the use of

In Agrobacterium-mediated recombination, the plasmid construct contains T-DNA, DNA which is responsible for insertion of the DNA into the host plants genome. This plasmid is transformed into Agrobacterium containing no plasmids prior to infecting the plant cells. The Agrobacterium will then naturally insert the genetic material into the plant cells.^[64] In biolistics transformation particles of gold or tungsten are coated with DNA and then shot into young plant cells or plant embryos. Some genetic material will enter the cells and transform them. This method can be used on plants that are not susceptible to Agrobacterium infection and also allows transformation of plant plastids. Another transformation method for plant and animal cells is electroporation. Electroporation involves subjecting the plant or animal cell to an electric shock, which can make the cell membrane permeable to plasmid DNA. In some cases the electroporated cells will incorporate the DNA into their genome. Due to the damage caused to the cells and DNA the transformation efficiency of biolistics and electroporation is lower than agrobacterial mediated transformation and microinjection.^[65]

Only about 1% of bacteria are naturally capable of taking up foreign DNA. However, this ability can be induced in other bacteria via stress (e.g. thermal or electric shock), thereby increasing the cell membrane's permeability to DNA; up-taken DNA can either integrate with the genome or exist as extrachromosomal DNA. DNA is generally inserted into animal cells using microinjection, where it can be injected through the cell's nuclear envelope directly into the nucleus or through the use of viral vectors.^[62] In plants the DNA is generally inserted using Agrobacterium-mediated recombination or biolistics.^[63]

A. tumefaciens attaching itself to a carrot cell

Transformation

The most common form of genetic engineering involves inserting new genetic material randomly within the host genome. Other techniques allow new genetic material to be inserted at a specific location in the host genome or generate mutations at desired genomic loci capable of knocking out endogenous genes. The technique of gene targeting uses homologous recombination to target desired changes to a specific endogenous gene. This tends to occur at a relatively low frequency in plants and animals and generally requires the use of selectable markers. The frequency of gene targeting can be greatly enhanced with the use of engineered nucleases such as zinc finger nucleases,^[54][55] engineered homing endonucleases,^[56][57] or nucleases created from TAL effectors.^[58][59] In addition to enhancing gene targeting, engineered nucleases can also be used to introduce mutations at endogenous genes that generate a gene knockout.^[60][61]

The gene to be inserted into the genetically modified organism must be combined with other genetic elements in order for it to work properly. The gene can also be modified at this stage for better expression or effectiveness. As well as the gene to be inserted most recombinant DNA techniques, such as restriction digests, ligations and molecular cloning.^[53] The manipulation of the DNA generally occurs within a plasmid.

The first step is to choose and isolate the gene that will be inserted into the genetically modified organism. As of 2012, most commercialised GM plants have genes transferred into them that provide protection against insects or tolerance to herbicides.^[49] The gene can be isolated using genome has been well studied it may be present in a genetic library. If the DNA sequence is known, but no copies of the gene are available, it can be artificially synthesized.^[52]

Process

In 2010, scientists at the J. Craig Venter Institute, announced that they had created the first synthetic bacterial genome. The researchers added the new genome to bacterial cells and selected for cells that contained the new genome. To do this the cells undergoes a process called resolution, where during bacterial cell division one new cell receives the original DNA genome of the bacteria, whilst the other receives the new synthetic genome. When this cell replicates it uses the synthetic genome as its template. The resulting bacterium the researchers developed, named Synthia, was the world's first synthetic life form.^[47][48]

In the late 1980s and early 1990s, guidance on assessing the safety of genetically engineered plants and food emerged from organizations including the FAO and WHO.^{[43][44][45][46]}

The first field trials of genetically engineered plants occurred in France and the USA in 1986, tobacco plants were engineered to be resistant to herbicides.^[37] The People’s Republic of China was the first country to commercialize transgenic plants, introducing a virus-resistant tobacco in 1992.^[38] In 1994 Calgene attained approval to commercially release the Flavr Savr tomato, a tomato engineered to have a longer shelf life.^[39] In 1994, the European Union approved tobacco engineered to be resistant to the herbicide bromoxynil, making it the first genetically engineered crop commercialized in Europe.^[40] In 1995, Bt Potato was approved safe by the Environmental Protection Agency, after having been approved by the FDA, making it the first pesticide producing crop to be approved in the USA.^[41] In 2009 11 transgenic crops were grown commercially in 25 countries, the largest of which by area grown were the USA, Brazil, Argentina, India, Canada, China, Paraguay and South Africa.^[42]

^[35] Both test fields were attacked by activist groups the night before the tests occurred: "The world's first trial site attracted the world's first field trasher".^[36] when a strawberry field and a potato field in California were sprayed with it.[35] In the 1970s graduate student Steven Lindow of the

In 1976 Genentech, the first genetic engineering company, was founded by Herbert Boyer and Robert Swanson and a year later the company produced a human protein (somatostatin) in E.coli. Genentech announced the production of genetically engineered human insulin in 1978.^[30] In 1980, the U.S. Supreme Court in the Diamond v. Chakrabarty case ruled that genetically altered life could be patented.^[31] The insulin produced by bacteria, branded humulin, was approved for release by the Food and Drug Administration in 1982.^[32]

In 1972 antibiotic resistance genes into the plasmid of an E. coli bacterium.^[25][26] A year later Rudolf Jaenisch created a transgenic mouse by introducing foreign DNA into its embryo, making it the world’s first transgenic animal.^[27] These achievements led to concerns in the scientific community about potential risks from genetic engineering, which were first discussed in depth at the Asilomar Conference in 1975. One of the main recommendations from this meeting was that government oversight of recombinant DNA research should be established until the technology was deemed safe.^[28][29]

In 1974 Rudolf Jaenisch created the first GM animal.

Humans have altered the genomes of species for thousands of years through artificial selection and more recently mutagenesis. Genetic engineering as the direct manipulation of DNA by humans outside breeding and mutations has only existed since the 1970s. The term "genetic engineering" was first coined by Jack Williamson in his science fiction novel Dragon's Island, published in 1951,^[22] one year before DNA's role in heredity was confirmed by Alfred Hershey and Martha Chase,^[23] and two years before James Watson and Francis Crick showed that the DNA molecule has a double-helix structure.

History

Plants, animals or micro organisms that have changed through genetic engineering are termed genetically modified organisms or GMOs.^[16] Bacteria were the first organisms to be genetically modified. Plasmid DNA containing new genes can be inserted into the bacterial cell and the bacteria will then express those genes. These genes can code for medicines or enzymes that process food and other substrates.^[17][18] Plants have been modified for insect protection, herbicide resistance, virus resistance, enhanced nutrition, tolerance to environmental pressures and the production of edible vaccines.^[19] Most commercialised GMO's are insect resistant and/or herbicide tolerant crop plants.^[20] Genetically modified animals have been used for research, model animals and the production of agricultural or pharmaceutical products. They include animals with genes knocked out, increased susceptibility to disease, hormones for extra growth and the ability to express proteins in their milk.^[21]

Genetically modified organisms

are preferred. transgenic is not commonly used; more specific terms such as genetic engineering Within the scientific community, the term ^[15][14][13]) or genetic engineering.mutation breeding, cell fusion, selective breeding The Canadian regulatory system is based on whether a product has novel features regardless of method of origin. In other words, a product is regulated as genetically modified if it carries some trait not previously found in the species whether it was generated using traditional breeding methods (e.g., ^[12][11] with genetic engineering while within the United States of America it can also refer to conventional breeding methods.synonymous In Europe genetic modification is [10] If genetic material from another species is added to the host, the resulting organism is called

[8]