Transgenesis: Difference between revisions
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#REDIRECT[[Gene delivery]] |
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{{Refimprove|date=April 2013}} |
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'''Transgenesis''' is the process of introducing an [[Exogeny|exogenous]] gene—called a [[transgene]]—into a [[living organism]] so that the organism will exhibit a new property and transmit that property to its [[offspring]]. Transgenesis can be facilitated by [[liposome]]s, [[enzyme]]s, [[plasmid vector]]s, [[viral vector]]s, [[Microinjection#Pronuclear injection|pronuclear injection]], [[protoplast fusion]], and [[gene gun|ballistic DNA injection]]. Transgenesis can occur in nature.<ref>{{Cite web|url=http://www.the-scientist.com/?articles.view/articleNo/44016/title/Parasite-s-Genes-Persist-in-Host-Genomes/|title=Parasite's Genes Persist in Host Genomes|last=Shaikh-Lesko|first=Rina|date=2015-09-17|website=The Scientist|access-date=2016-07-13}}</ref><ref>{{cite journal|last1=Kyndt|first1=Tina|last2=Quispea|first2=Dora|last3=Zhaic|first3=Hong|last4=Jarretd|first4=Robert|last5=Ghislainb|first5=Marc|last6=Liuc|first6=Qingchang|last7=Gheysena|first7=Godelieve|last8=Kreuzeb|first8=Jan F.|title=The genome of cultivated sweet potato contains Agrobacterium T-DNAs with expressed genes: An example of a naturally transgenic food crop|journal=Proceedings of the National Academy of Sciences of the United States of America|date=20 April 2015|doi=10.1073/pnas.1419685112|url=http://www.pnas.org/content/early/2015/04/14/1419685112.abstract|accessdate=23 April 2015|volume=112|pages=5844–5849|pmid=25902487|pmc=4426443}}</ref> |
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[[Transgenic organism]]s are able to express foreign genes because the [[genetic code]] is similar for all organisms. This means that a specific [[DNA sequence]] will code for the same [[protein]] in all organisms. Due to this similarity in protein sequence, scientists can cut DNA at these common protein points and add other genes. An example of this is the "[[genetically modified mouse|super mice]]" of the 1980s. These mice were able to produce the human protein tPA to treat blood clots. |
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==Using plasmids from bacteria== |
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The most common type of transgenesis research is done with bacteria and viruses which are able to replicate foreign DNA.<ref name="fasHistoryTransgenics" /> The [[plasmid]] DNA is cut using [[restriction enzyme]]s, while the DNA to be copied is also cut with the same restriction enzyme, producing complementary [[sticky end|sticky-ends]]. This allows the foreign DNA to [[Nucleic acid hybridisation|hybridise]] with the plasmid DNA and be sealed by DNA [[enzyme|ligase enzyme]], creating a genetic code not normally found in nature. Altered DNA is inserted into plasmids for replication.<ref name="redway" /> |
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==Gene transfer technology== |
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===DNA microinjection=== |
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The Desired gene construct is injected in the [[pronucleus]] of a reproductive cell using a glass needle around 0.5 to 5 micrometers in diameter. The manipulated cell is cultured [[in vitro]] to develop to a specific embryonic phase, is then transferred to a recipient female. DNA microinjection does not have a high success rate (roughly 2% of all injected subjects), even if the new DNA is incorporated in the [[genome]], if it is not accepted by the germ-line the new traits will not appear in their offspring. If DNA is injected in multiple sites the chances of over-expression increase.<ref name="margawati2003" /> |
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===Retrovirus-mediated gene transfer=== |
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A [[retrovirus]] is a virus that carries its genetic material in the form of [[RNA]] rather than DNA. Retroviruses are used as vectors to transfer genetic material into the host cell. The result is a [[chimera (genetics)|chimera]], an organism consisting of tissues or parts of diverse genetic constitution. Chimeras are inbred for as many as 20 generations until [[homozygous]] genetic offspring are born.<ref name="margawati2003" /> |
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=== Restriction enzyme mediated integration === |
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[[Restriction enzyme mediated integration]] (REMI) is a technique for integrating [[DNA]] (linearised plasmid) into the genome sites that have been generated by the same restriction enzyme used for the DNA linearisation. The plasmid integration occurs at the corresponding sites in the genome, often by regenerating the recognition sites by same the restriction enzyme used for plasmid linearisation. |
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===Stem cell transgenesis=== |
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====Multipotent stem cell transgenesis==== |
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[[Multipotent]] stem cells can only differentiate into a limited number of therapeutically useful cell types, nevertheless their safety and relative lack of complexity to us have resulted in the vast majority of current personalized cellular therapeutics involving multipotent stem cells (typically mesenchymal stem cells from adipose tissue).<ref>clinicaltrials.org</ref> |
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====Pluripotent stem cell transgenesis==== |
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Transgenic vectors can be delivered randomly{{citation needed|date=July 2014}}, or targeted to a specific genomic location, such as a safe harbor {{citation needed|date=July 2014}}. Scientists have performed research and technology development to provide the tools necessary to permit safe and effective pluripotent stem cell (PSC) transgenesis.<ref>{{cite journal |author=Capecchi MR |title=Gene targeting in mice: functional analysis of the mammalian genome for the twenty-first century |journal=Nat. Rev. Genet. |volume=6 |issue=6 |pages=507–12 |date=June 2005 |pmid=15931173 |doi=10.1038/nrg1619 }}</ref><ref>{{cite journal |vauthors=Cong L, Ran FA, Cox D, etal |title=Multiplex genome engineering using CRISPR/Cas systems |journal=Science |volume=339 |issue=6121 |pages=819–23 |date=February 2013 |pmid=23287718 |pmc=3795411 |doi=10.1126/science.1231143 |url=http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=23287718}}</ref><ref>{{cite journal |vauthors=DiCarlo JE, Norville JE, Mali P, Rios X, Aach J, Church GM |title=Genome engineering in ''Saccharomyces cerevisiae'' using CRISPR-Cas systems |journal=Nucleic Acids Res. |volume=41 |issue=7 |pages=4336–43 |date=April 2013 |pmid=23460208 |pmc=3627607 |doi=10.1093/nar/gkt135 |url=http://nar.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=23460208}}</ref><ref>{{cite journal |vauthors=Friedland AE, Tzur YB, Esvelt KM, Colaiácovo MP, Church GM, Calarco JA |title=Heritable genome editing in ''C. elegans'' via a CRISPR-Cas9 system |journal=Nat. Methods |volume=10 |issue=8 |pages=741–3 |date=August 2013 |pmid=23817069 |pmc=3822328 |doi=10.1038/nmeth.2532 }}</ref><ref>{{cite journal |vauthors=Hwang WY, Fu Y, Reyon D, etal |title=Efficient genome editing in zebrafish using a CRISPR-Cas system |journal=Nat. Biotechnol. |volume=31 |issue=3 |pages=227–9 |date=March 2013 |pmid=23360964 |pmc=3686313 |doi=10.1038/nbt.2501 }}</ref><ref>{{cite journal |vauthors=Nguyen HN, Reijo Pera RA |title=Metaphase spreads and spectral karyotyping of human embryonic stem cells |journal=CSH Protoc |pages=pdb.prot5047 |year=2008 |pmid=21356916 |url=http://cshprotocols.cshlp.org/cgi/pmidlookup?view=long&pmid=21356916}}</ref><ref>{{cite journal |vauthors=Mali P, Yang L, Esvelt KM, etal |title=RNA-guided human genome engineering via Cas9 |journal=Science |volume=339 |issue=6121 |pages=823–6 |date=February 2013 |pmid=23287722 |pmc=3712628 |doi=10.1126/science.1232033 |url=http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=23287722}}</ref><ref>{{cite journal |vauthors=Xue H, Wu J, Li S, Rao MS, Liu Y |title=Genetic Modification in Human Pluripotent Stem Cells by Homologous Recombination and CRISPR/Cas9 System |journal=Methods Mol. Biol. |volume= |issue= |pages= |date=March 2014 |pmid=24615461 |doi=10.1007/7651_2014_73 }}</ref> |
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====Totipotent stem cell transgenesis==== |
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The manipulated gene construct is inserted into [[totipotent stem cells]], cells which can develop into any specialized cell. Cells containing the desired DNA are incorporated into the host’s [[embryo]], resulting in a chimeric animal. Unlike the other two methods of injection which require live transgenic offspring for testing, embryonic cell transfer can be tested at the cell stage. |
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==Applications== |
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===Pharming=== |
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{{main|Pharming (genetics)}} |
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Pharming, a [[portmanteau]] of "farming" and "[[pharmaceutical]]", refers to the use of [[genetic engineering]] to insert [[genes]] that code for useful pharmaceuticals into host animals or plants that would otherwise not express those genes. Pharming has gained application in [[biotechnology]] since the development of transgenic "super mice" in 1982. "Super mice" were genetically altered to produce the human drug, tPA ([[tissue plasminogen activator]] to treat [[blood clots]]), in 1987.<ref name="redway" /> Since then, "super mice" pharming has come a long way. Using [[RNA interference]], scientists have produced a cow whose milk contains increased amounts of [[casein]], a protein used to make cheese and other foods, and almost no [[beta-lactoglobulin]], a component in milk whey protein that causes allergies.<ref name="lopatto2012" /> |
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'''Pharming examples:'''<ref>{{cite web |author=Buy M |title=Transgenic Animals |date=1997 |work=CCAC Resource Supplement |publisher=Canadian Council on Animal Care (CCAC) |url=http://people.ucalgary.ca/~browder/transgenic.html}}</ref> |
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*[[Haemoglobin]] as a blood substitute |
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*Human protein C anticoagulant |
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*Alpha-1 antitrypsin ([[Alpha 1-antitrypsin|AAT]]) for treatment of AAT deficiency |
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*[[Insulin]] for diabetes treatment |
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*[[Vaccine]]s (antigens) |
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*[[Growth hormones]] for treatment of deficiencies |
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*Factor VIII blood clotting factor |
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*Factor IX blood clotting factor |
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*[[Fibrinogen]] blood clotting factor |
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*[[Lactoferrin]] as an infant formula additive |
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===Medical=== |
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Transgenesis can be used to neutralize genes that would normally prevent [[xenotransplantation]]. For example, a [[protein]] found in pigs can cause humans to reject their transplanted [[organ (anatomy)|organs]]. This protein can be replaced by a similar human genome to prevent the rejection.<ref name="actionbioscience">{{cite web|url=http://www.actionbioscience.org/biotechnology/margawati.html|title=Actionbioscience | Transgenic Animals: Their Benefits To Human Welfare|publisher=actionbioscience.org|accessdate=November 29, 2014}}</ref> |
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==Ethical concerns== |
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Transgenesis has created certain ethical concerns. Examples include rights for animals that have been improved intellectually, legal ramifications, and possible health risks.<ref name="actionbioscience2">{{cite web|url=http://www.actionbioscience.org/biotechnology/glenn.html|title=Actionbioscience | Ethical Issues in Genetic Engineering and Transgenics|publisher=actionbioscience.org|accessdate=November 29, 2014}}</ref> |
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== Diagram == |
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[[Image:Breeding transgenesis cisgenesis.svg|thumb|center|700px|A diagram comparing the genetic changes achieved through conventional plant breeding, transgenesis and cisgenesis]]. |
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Note: New genotypes created with transgenic technologies also require multiple backcrossings. Furthermore, backcrossing does not account for the majority of time required to create, field test and release/commercialize a new variety. |
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==References== |
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{{Reflist|refs= |
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* <ref name="fasHistoryTransgenics">{{cite web | title=Mousepox Case Study — Module 4.0 | url=https://fas.org/biosecurity/education/dualuse/FAS_Jackson/1_A.html | deadurl=yes | publisher=[[Federation of American Scientists]] | at=History of Transgenics | archiveurl=https://web.archive.org/web/20070715054717/https://fas.org/biosecurity/education/dualuse/FAS_Jackson/1_A.html | archivedate=July 15, 2007 }}</ref> |
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* <ref name="lopatto2012">{{cite news | url=http://www.businessweek.com/news/2012-10-01/gene-modified-cow-makes-milk-rich-in-protein-study-finds | title=Gene-Modified Cow Makes Milk Rich in Protein, Study Finds | work=[[Bloomberg Businessweek]] | date=October 1, 2012 | author=Lopatto, Elizabeth | location=New York City | deadurl=no<!--present in archive.org-->}}</ref> |
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* <ref name="margawati2003">{{cite web | url=http://www.actionbioscience.org/biotech/margawati.html | title=Transgenic Animals: Their Benefits To Human Welfare | work=[[Actionbioscience]] | date=January 2003 | accessdate=June 29, 2014 | author=Margawati, Endang Tri | deadurl=no<!--cannot enter archive.org due to robots.txt-->}}</ref> |
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* <ref name="redway">{{cite web | url=http://users.wmin.ac.uk/~redwayk/lectures/transgenic.htm | title=Transgenic organisms | publisher=[[University of Westminster]] | work=Gene Manipulation & Recombinant DNA | accessdate=June 28, 2014 | author=Redway, Keith | deadurl=no<!--present in archive.org-->}}</ref> |
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}} |
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[[Category:Genetic engineering]] |
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Latest revision as of 04:09, 19 July 2018
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