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Published byChris Beams Modified over 9 years ago
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Transgenesis Transferring a gene(s) from one species to another Introduce desirable traits not normally be present in a species. Genetic modification
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Techniques used Restriction digestion (cut desired gene) Ligation (insert desired gene into vector) Whole animal OR Gene cloning
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GM Animals Modified DNA introduced into fertilised egg all new cells, including gamete producing cells are transgenic - will be inherited OR Normal gene inserted into somatic tissue to correct a genetic deficiency – not inherited (gene therapy) Livestock able to produce human proteins.
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Methods of animal transgenesis 1.electroporation 1.electroporation: brief electric shock opens pores in plasma membrane and allows DNA to be taken up from medium 2.viral carrier 2.viral carrier: transduction after viral DNA is made harmless 3.lipofection 3.lipofection: DNA coated with minute lipid vesicles (liposomes) which are endocytosed 4.microinjection 4.microinjection: using micropipette(low success)
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Cows Milk Cows can produce relatively large quantities of protein. Inserting genes into the cows to produce modified milk can be relatively easy. Genes inserted to produce milk with improved: calf nutrition and disease resistance resistance against mastitis benefits for human health commercial possibilities
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Example Application Human Myelin Basic Protein - Human Myelin Basic Protein - essential protein in the myelin sheath that insulates and protects neurones – absent in Multiple Sclerosis. previously from blood products or cadavers – slow, expensive and could be contaminated GM milk protein extracted therapeutic drugs fast production of large amounts of protein cheaper than previous methods less objectionable than cadavers and blood??
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Example Application Casein Casein is a naturally occurring milk protein used in cheese production Gene inserted so cows milk contains more casein more milk solids more efficient, cost-effective cheese production products such as infant milk powder production could become cheaper BUT currently benefits offset by cost weight gain / diseases associated with excess casein
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Example Application Chymosin Chymosin (rennin) used to manufacture food products that require clotted milk previously obtained from calf stomachs Now incorporated into transgenic bacteria / yeast totally hygienic large quantities any time of year (yeast reproduce freely) identical to natural calf chymosin more acceptable to vegetarians? BUT: Yeast/bacteria may mutate and not function correctly
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GM Plants Improved characteristics Improved characteristics such as resistance to pests and diseases Modified characteristics Modified characteristics such as vitamin A synthesis in crops – nutritionally superior Increased productivity Increased productivity - GM crops larger Anti-GM lobbyists: risk of contamination of organic farms, creation of super-weeds and the potential extinction of wild plants.
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Methods of Plant transgenesis Protoplast fusion Protoplast fusion – cell with cell wall digested = protoplast (2 protoplasts fuse double DNA) Biolistics/ DNA gun Biolistics/ DNA gun - microscopic particles of gold or tungsten coated in transgene DNA propelled into cell Plasmid or viral vectors Plasmid or viral vectors - recombinant DNA transferred via vectors. None of these methods are fully successful
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Protoplast fusion Enzymes digest cell walls 2 diploid cells fuse cell with double DNA
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Protoplast fusion
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Particle gun method vector method
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Agrobacterium tumefaciens Gall disease bacterium enters wounded tissue inserts tumour-inducing (Ti) plasmid into plant T-DNA incorporated into host chromosome stimulates cell division Plasmid is prepared by: removing the tumor gene adding antibiotic resistance gene (as a marker) Medium with antibiotic kills off unmodified cells
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gall tumour caused by agrobacterium tumefaciens
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