Transgenesis Transferring a gene(s) from one species to another Introduce desirable traits not...
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![Page 1: Transgenesis Transferring a gene(s) from one species to another Introduce desirable traits not normally be present in a species. Genetic modification.](https://reader038.fdocuments.us/reader038/viewer/2022103122/56649cad5503460f9496f839/html5/thumbnails/1.jpg)
TransgenesisTransferring 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: brief electric shock opens pores in plasma membrane and allows DNA to be taken up from medium
2. viral carrier: transduction after viral DNA is made harmless
3. lipofection: DNA coated with minute lipid vesicles (liposomes) which are endocytosed
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 ApplicationHuman 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 ApplicationCasein 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 ApplicationChymosin (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 such as resistance to pests and diseases
• Modified characteristics such as vitamin A synthesis in crops – nutritionally superior
• 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 – cell with cell wall digested =
protoplast (2 protoplasts fuse double DNA)
• Biolistics/ DNA gun - microscopic particles of gold or tungsten coated in transgene DNA propelled into cell
• 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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Pro
top
last
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on
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Part
icle
gun
meth
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vect
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meth
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Agrobacterium tumefaciensGall 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