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Transgenic animals


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transgenic animals

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Transgenic animals

  1. 1. TRANSGENIC ANIMALS By Dr.Elza Joy Munjely
  2. 2. DEFINITION • Carries a foreign gene that has been deliberately inserted into its genome • Foreign gene is constructed using recombinant DNA technology
  3. 3. WHY CREATE THEM? • Improve livestock animals • Use of animals as bioreactors • Production of pharmaceutical drugs • Used as Model Organisms in research
  4. 4. CREATION PRINCIPLE • Inserting a foreign gene/genes into an animal • The inserted genes are called Transgenes • Genes must be transmitted through the germ line
  6. 6. STEP-1 CONSTRUCTION OF A TRANSGENE Target gene – transgene • Promoter-regulatory sequence • Coding sequence • Poly A tail Transgene Structure
  8. 8. 1. DNA Microinjection 2. Retrovirus-Mediated Gene Transfer 3. Embryonic Stem Cell-Mediated Gene Transfer 4. Linker Based Sperm-Mediated Gene Transfer There are 4 basic methods:
  9. 9. 1) DNA Microinjection • Eggs are harvested from the animal • Transfer the desired gene into the pronucleus of the sperm • Egg is then fertilized invitro & cultured to develop embryonic phase • Transferred to the recipient female
  10. 10. 2) Retrovirus-Mediated Gene Transfer • A retrovirus is an animal virus that contain RNA that encodes for DNA. • Retroviruses transfer genetic material into the host cell to produce Chimeras- animal with mixed DNA • Chimeras are inbred until homozygous transgenic offspring are born
  11. 11. Vector binds to cell membrane Vector packaged In vesicle Vesicle breaks down Releasing vector Vector injects new Gene into nucleus Modified DNA injected Into vector Cell makes protien using new gene Viral DNA Viral DNA New gene
  12. 12. 3) Embryonic Stem Cell Method • Desired genes are inserted into the totipotent stem cells • Cells transform to express the desired gene is selected & injected into the inner cell mass of the organism blastocyst • Embriyo is then implanted into foster mother • Multiple matings within generations is done to get a homozygous offspring
  13. 13. Alterations made to Stem cells in culture Fertilised egg blastocyst Blastocyst implanted into Foster mother Mutated Stem cells Injected Into blastocyst
  14. 14. 4) Linker Based Sperm-Mediated Gene Transfer • Sperm carrying the foreign gene, fertilizes the egg where foreign gene is incorporated into the genome
  15. 15. STEP 3 Screening for transgenic positives • Transgenic progenies are screened by PCR to examine the site of incorporation of the gene
  16. 16. STEP 4 Further animal breeding is done to obtain maximal expression • Heterozygous offsprings are mated to form homozygous strains.
  17. 17. Examples of “Transgenic Animals”
  18. 18. Transgenic Cow • Carry extra copies of two types of Casein genes • 13% more milk protein • Milk -more nutritious • Currently the milk from these animals is under FDA review
  19. 19. EnviroPig • Can digest plant phosphorus more efficiently • Have Phytase enzyme in their salivary glands • Phytic acid in the pig meal is degraded releasing phosphorus which is absorbed by the pig • Pig waste is a major pollutant Pig for organ transplant – Pigs with human genes – decrease the chance of organ rejection by human body.
  20. 20. Transgenic Fish • Salmon/trout- can grow up to 6 times faster than wild-type fish as they have extra copies of Growth Hormone (GH) gene • Ornamental GloFish have red, green, yellow, and orange fluorescent color,available as a pet.
  21. 21. Transgenic Mice • Most widely used Model Animal to detect gene expression • Used in Knock-Out technology to detect gene function
  22. 22. GENE KNOCKOUT • Technique for selectively inactivating a gene by replacing it with a mutant allele • Gene knockout mice are model systems for studying inherited human diseases
  23. 23. • Alzheimer’s mouse – Mouse made by introducing amyloid precursor gene into fertilized egg of mice. • Oncomouse – Mouse model to study cancer – Made by inserting activated oncogenes. • Smart mouse – Biological model engineered to overexpress NR2B receptor in the synaptic pathway. – This makes the mice learn faster like juveniles throughout their lives.
  24. 24. Transgenic Monkey • ANDI, the first transgenic rhesus monkey born on October 2nd 2000, has GFP gene • Glow in Dark Monkeys also have GFP and glow under UV light • Model for studying autism,Alzhiemers,MND etc
  25. 25. Transgenic Rabbit • Alba, the EGFP (enhanced GFP) bunny created in 2000 as a transgenic artwork • Has GFP gene and glows when exposed to Blue light • Used as model for cardiovascular diseases,AIDS & cancer • As bioreactors for human protiens
  26. 26. Transgenic Cats • Transgenic cats contain red and green fluorescent protein
  27. 27. Transgenic Goats • Silk gene from spiders is transferred to goats • Each goat produces several grams of silk protein in her milk
  28. 28. Some Ethical Concerns • Use of animals in research causes great suffering to the animals • Using animals for the production of pharmaceutical proteins will reduce them to mere factories • Animals should have the same basic rights as human beings • Each biological species has a right to exist as a separate identifiable entity • Animal model is not patentable in India
  29. 29. ISSUES RELATED TO TRANSGENIC TECHNOLOGY • Blurring the lines between species by creating transgenic combinations. • Health risks associated with transgenics. • Long term effects on the environment when transgenic animals are released into the field. • Various bioethicist argue that it is wrong to create animals that would suffer as a result of genetic alteration.
  30. 30. IMPORTANCE OF TRANSGENIC ANIMALS • Medical importance – Disease model – Bioreactors for pharmaceuticals – Xenotransplantation • Agricultural importance – Disease resistant animals – For improving quality and quantity of milk, meat, eggs and wool production • Industrial importance – Toxicity sensitive transgenic animals to test chemicals. – Spider silk in milk of goat
  31. 31. NUDE MICE
  32. 32. NUDE MICE • First discovered in 1962 by Dr. N. R. Grist at Ruchill Hospital's Brownlee virology laboratory in Glasgow • laboratory mouse from a strain with a genetic mutation • Spontaneous deletion in the FOXN1 gene.
  33. 33. NUDE MICE • Deteriorated or absent thymus • Inhibited immune system due to a greatly reduced number of T cells • Phenotype-lack of body hair
  34. 34. Without the thymus gland ,these mice are unable to – Kill virus infected cells/malignant cells – Reject tissue grafts, even xenografts – Form Ab (dependent on T cells) – Develop hypersensitivity responses
  35. 35. USES 1. Testing anticancer therapies for human neoplasms 2. Study of leukaemias,solid tumours 3. Invivo study of metastasis 4. Provided an insight into the functioning of immune system, T cell differentiation,specific cellular reactions 5. Study of AIDS & other immunodeficiencies 6. Thermogenesis in imm. def. states