7 Chapter Animal Biotechnology
BTEC 3301
Dolly the sheep
Dollywascreatedbyagriculturalresearchscientists, whowerebeingfundedtomaketheperfectsheep,for thepurposesofmoreefficientagriculturalproduction. Thename"Dolly"camefromasuggestionbythe stockmenwhohelpedintheprocess,inhonorofDolly Parton,becausetheclonedcellwasamammarycell Afterthecloningwassuccessfullydemonstratedby Dollycreators,manyotherlargemammalshavebeen cloned,includinghorsesandbulls.
Dollywhobecamethefirstfamousadultclonedsheep wassuccessfullyclonedin1996,(July1996toFeb 2003)wasthefirstmammaltohavebeensuccessfully clonedfromadultcells. ShewascreatedatRoslinInstituteScotlandandlived thereuntilherdeathnearlysevenyearslater. Dollywasputdownon Feb142003,duetocomplicationsfromalung infection.
Refer: Pg 159 Fig7.7 for the process.
Transgenic Animals:
Animalbiotechnologyisthefieldtoengineer transgenicanimals,i.e.,animalsthatcarry genesfromotherspecies. Thetechnologyhasalreadyproducedtransgenic animalssuchasmice,rats,rabbits,pigs,sheep, andcows
What is a transgenic animal?
A transgenic animal is one whose genome has been changed to carry genes from other species. Forexample,anembryocanhaveanextra, functioninggenefromanothersourceartificially introducedintoit,orageneintroducedwhichcan knockoutthefunctioningofanotherparticulargene intheembryo
AnimalsthathavetheirDNA manipulatedinthiswayareknownas transgenicanimals. Transgenicanimalsareusefulasdisease modelsandproducersofsubstancesfor humanwelfare
Why are these animals being produced?
Sometransgenicanimalsareproducedforspecific economictraits.Forexample,transgeniccattlewere createdtoproducemilkcontainingparticularhuman proteins,whichmayhelpinthetreatmentofhuman emphysema(Alungdiseasewhichinvolvesdamage totheairsacs(alveoli)inthelungs)
Othertransgenicanimalsareproducedasdisease models(animalsgeneticallymanipulatedtoexhibit diseasesymptomssothateffectivetreatmentcanbe studied TheOncoMouse or the Harvard mouse,carryingagenethatpromotesthe developmentofvarioushumancancers
How are transgenic animals produced?
DNA microinjection:
Introducing the transgene DNA directly into the zygote at an early stage of development. No vector required
Retrovirus-mediated gene transfer:
Infecting mouse embryo with a retrovirus which carry the new gene. Using virus as a vector.
Embryonic stem cell-mediated gene transfer:
The blastocyst (inner layer of a fertilized egg) is harvested and mixed with recombinant DNA and inserted back in the blastocyst
Sperm-mediated transfer:
Use of Linker protein" to attach DNA to sperm which transfer the new DNA during fertilization. Gene gun: As described in Chapter 6.
Embryonic stem cell-mediated gene transfer:
This method involves:
isolation of totipotent stem cells (stem cells that can develop into any type of specialized cell) from embryos the desired gene is inserted into these cells Cells containing the desired DNA are incorporated into the host's embryo.
Assignment for class: Stem cell Research.
Stem cell Research
Improving Agricultural Products with Transgenics
Transgenic technology holds great potential in agriculture, medicine, and industry
The benefits of these animals to human welfare can be grouped into areas: Agriculture Medicine Industry
1. Agricultural Applications A) Breeding:
Traditional cross breeding have been used for ages to create chickens, cows, pigs etc. Farmers have always used selective breeding to produce animals that exhibit desired traits (e.g., increased milk production, high growth rate). Traditional breeding is a timeconsuming, difficult task.
Researchers have now used gene transfer to improve the productivity of livestock. Now it is possible to develop traits in animals in a shorter time and with more precision. It also offers farmers an easy way to increase yields.
Scientists can improve the size of livestock genetically. Transgenic cows exist that produce more milk or milk with less lactose or cholesterol. Transgenic cows have been used to produce milk which are richer in proteins and lower in fat.
B) Quality:
Herman, a transgenic bull carries a human gene for Lactoferrin (gene responsible for higher iron content) Pigs and cattle that have more meat on them. Sheep that grow more wool. Eggs can be made healthier with high quality protein.
C) Disease resistance:
Disease-resistant livestock is not a reality just yet. But there has been improvement in disease reduction in animals. The Foot- and- Mouth disease in England in 2000 led to destruction of herds of cattle, sheep and goat.
Scientists are attempting to produce disease-resistant animals, such as influenza-resistant pigs, but a very limited number of genes are currently known to be responsible for resistance to diseases in farm animals. Transgenic disease protection promises a long term cost effective method of battling animal diseases.
2. Medical Applications
A)Xenotransplantation:
Transplant organs may soon come from transgenic animals. Transgenic pigs may provide the transplant organs needed to alleviate the shortage of organs donor
Xenotransplantation is hampered by a pig protein that can cause donor rejection but research is underway to remove the pig protein and replace it with a human protein. Milk-producing transgenic animals are especially useful for medicines.
B) Nutritional supplements and pharmaceuticals:
Products such as insulin, growth hormone, and blood anti-clotting factors may soon be or have already been obtained from the milk of transgenic cows, sheep, or goats. The first transgenic cow (Rosie ) produced human protein-enriched milk at 2.4 grams per liter.
This transgenic milk is a more nutritionally balanced product than natural milk and could be given to babies or the elderly with special nutritional or digestive needs. A transgenic cow exists that produces a substance to help human red cells grow.
C) Human gene therapy:
Human gene therapy involves adding a normal copy of a gene (transgene) to the genome of a person carrying defective copies of the gene. Finland produced a calf with a gene that makes the substance that promotes the growth of red cells in humans.
3. Industrial Applications
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By extracting polymer strands from the milk and weaving them into thread, the scientists can create a light, tough, flexible material that could be used in such applications as military uniforms, medical microsutures, and tennis racket strings. Biosteel an is extraordinary new product that may be soon used in bullet proof vests and in suture silk for stitching wounds. Animals have been used as Bioreactors to produce proteins. Genes for desired proteins are introduced via transgenics to the target cells.
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The target cells are cloned and several such cells are raised into adults. These adults may produce milk or eggs (due to the presence of introduced gene rich in desired protein). Toxicity-sensitive transgenic animals have been produced for chemical safety testing. Microorganisms have been engineered to produce a wide variety of proteins, which in turn can produce enzymes that can speed up industrial chemical reactions.
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Transgenic animals have been used to produce pharmaceutical protein: example a human gene called AT III has been transferred to goats. Goats milk contain this protein that prevents blood clotting (goats multiply faster than cows) Hen bioreactor eggs are used to enrich protein by recombinant DNA technology.
What are the ethical concerns surrounding transgenesis?
Ethical concern is ever increasing as the technology grows, including the issue of lab animal welfare
These ethical issues include questions such as:
Should there be universal protocols for transgenesis? Should such protocols demand that only the most promising research be permitted?
Ishumanwelfaretheonlyconsideration? Whataboutthewelfareofotherlifeforms? Shouldscientistsfocusoninvitro(culturedinalab) transgenicmethodsratherthan,orbefore,usinglive animalstoalleviateanimalsuffering?
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Willtransgenicanimalsradicallychangethe directionofevolution,whichmayresultindrastic consequencesfornatureandhumansalike? Shouldpatentsbeallowedontransgenicanimals, whichmayhamperthefreeexchangeofscientific research??
A summary of Animal Cloning
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Although there has been limited success in cloning some animals, it's still seen as a viable technology. Ever since the announcement of the birth of Dolly three years ago, additional sheep, cows, goats, pigs and mice have been cloned. So far, most cloned animals die just
before or after birth.
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There are still obvious problems as evidenced from the numerous deaths of cloned animals that occur just before or after birth. Cloning is a big first step. Genetic manipulation of cloned animals is the future direction of the cloning frontier.
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Cloning can produce genetically identical laboratory animals which can be used as models for human disease. No live dog clones have yet been reported, the company PerPETuate, Inc. (Connecticut) is freezing tissue from family pets for the future. Cells could be harvested from early embryos to provide cell and tissue replacement without the hazards of transplantation rejection.
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The cloning of human embryos for reproductive purposes is illegal at this time. Yet it is still important to examine the consequences and the likelihood of this scenario. The media may dream up and forecast robotic cloned armies of Hitler; however, identical twins illustrate that being genetically identical does not remove their humanness.
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At any rate, there have been significant difficulties with cloning primates, including an extremely low success rate and a high number of abnormalities. These results make it unacceptable to attempt human cloning at this moment in time. Cloning has opened many doors that could lead to remarkable medical advancements but, as with all new technologies, it will be accompanied by ethical and social
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Today's successes will pave the road to improving efficiencies and help add to the basic understanding of our cells. Even Dolly's creator, Ian Wilmut, is focusing less on sheep and more on understanding the mechanism of reprogramming our genetic material!.
What are stem cells? Additional reading
Keep update with political issues on stem cells research including Christopher R...