Cloning 100809065228-phpapp01

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Cloning 100809065228-phpapp01

  1. 1. CLONINGAn Overview
  2. 2. GROUP MEMBERS• HASSAN TARIQ (2008-EE-180) Introduction and Overview Cloning in Nature• ZAIR HUSSAIN (2008-EE-177) History of Cloning• SAQIB SAEED (2008-EE-168) How scientists clone cells• UMAIR MAQBOOL (2008-EE-178) Stem cells technology Benefits of Cloning
  3. 3. Introduction and overview
  4. 4. Introduction• Cloning: Creating copies of living matter• The term clone (from the Greek word klōn, meaning “twig”) had already been in use since the beginning of the 20th century in reference to plants• Clones have identical genetic makeup• Abundant in nature• Used by scientists to generate organisms with valuable traits
  5. 5. Historical Perspective• Farmers started using it thousands of years ago• Revolutionized in late 20th Century with the advent of genetic engineering
  6. 6. Cloning in Animals• To generate animals with desirable traits• To bolster endangered species• Maybe in near future, extinct animals can be resurrected
  7. 7. Industrial Perspective• Production of bacteria which can clean up environmental contamination• Animals which can produce commercial ingredients e.g. protein
  8. 8. Importance for Humans• Promises great advances in medicine• Biomedical scientists plan to create animals with human diseases, so that cures can be experimented safely
  9. 9. CLONING IN NATURE
  10. 10. In Bacteria and Plants• Originated in nature• Most organisms reproduce asexually• Unicellular organisms reproduce by fission, a cloning method• Plants like strawberries clone by producing runners
  11. 11. In Animals and Mammals• Some species of fish, shrimps, lizards and frogs produce by parthenogenesis- from Greek word parthenos (“virgin”) and genesis (“birth”)• Clones in mammals- genetic copies of each other
  12. 12. HISTORY OF CLONING
  13. 13. Initial Efforts• 1800’s- First try of using undifferentiated cells  Hans Dreisch separated a sea urchin embryo when it was just two cells  Both cells grew to adults• Early 1900’s- Hans Spemann extended Dreisch’s work to salamanders  Determined that nucleus from embryo cell could direct the development of a complete organism  Published his results in 1938  Proposed a “fantastical” experiment
  14. 14. Early Frog Experiments• 1952- Spemann’s idea realized by Robert Briggs and Thomas King  Used cell nuclear transfer to insert DNA from a frog embryo cell into an enucleated frog egg  Resulting embryo grew into an adult  Early experiments using cell nuclear transfer were successful only when donor DNA was taken from an embryonic cell
  15. 15. Early Frog Experiments (Gurdon’s Method)• 1962- John Gurdon began cloning experiments using non-embryonic cells  Cells from intestinal lining of tadpoles  Exposed a frog egg to ultraviolet light, which destroyed its nucleus  Removed the nucleus from the tadpole intestinal cell and implanted it in the enucleated egg  Egg grew into a tadpole that was genetically identical to the DNA-donating tadpole
  16. 16. Impact of Gurdon’s Research• Gurdon’s experiments captured the attention of the scientific community• Tools and techniques he developed for nuclear transfer are still used today• 1963- J. B. S. Haldane, in describing Gurdon’s results, became one of the first to use the word clone in reference to animals
  17. 17. Glitches of Gurdon’s Method• Tadpoles cloned in Gurdon’s experiments never survived to adulthood• Scientists now believe that cells used may not have been differentiated cells
  18. 18. Mammal Cloning (Initial Efforts)• Scientists turned their attention to cloning mammals• Proved even more complex than earlier cloning experiments on invertebrates and amphibians• 1977- Karl Illmensee reported cloning mice from cells derived from early embryos Illmensee’s findings were largely discredited because he used questionable laboratory techniques• Agricultural researchers tried to clone cattle using somatic cell nuclear transfer, but failed
  19. 19. Mammal Cloning (Breakthrough)• 1984- First mammal cloned  Danish biologist Steen Willadsen  Working at Cambridge University in England• Used nuclear transfer with DNA from early embryonic cells• Two years later, a team of researchers at the University of Wisconsin cloned a cow through a similar approach
  20. 20. Mammal Cloning (Further Developments)• 1990’s- Cloning techniques advanced rapidly• 1995- Two lambs cloned By Keith Campbell and Ian Wilmut at the Roslin Institute From embryonic cells; named Megan and Morag Scientists were able to keep the embryonic cells alive in culture for some time before beginning the cloning procedure• Enabled scientists to modify an embryonic cell’s genes in culture before cloning• Genetically modified livestock can be produced
  21. 21. Megan and Morag
  22. 22. HOW SCIENTISTS CLONE CELLS…BLASTOMERE SEPARATIONBLASTOCYST DIVISIONSOMATIC CELL NUCLEAR TRANSFER
  23. 23. Up till 1950’s• Initial Efforts- Letting a single cell divide in a laboratory dish by ‘mitosis’• Complex Techniques- Using animal embryos• 1950’s- Using cells that haven’t been differentiated yet (totipotent)
  24. 24. HOW SCIENTISTS CLONE CELLS…• BLASTOMERE SEPARATION• BLASTOCYST DIVISION• SOMATIC CELL NUCLEAR TRANSFER
  25. 25. Blastomere Separation• Fertilize an egg cell with a sperm cell in a laboratory dish till embryo is of about 4 cells• Outer coating of embryo removed• Placed in a solution to separate individual cells (Blastomeres)• Each blastomere cultured separately• Embryos implanted into surrogate mothers
  26. 26. HOW SCIENTISTS CLONE CELLS…• BLASTOMERE SEPARATION• BLASTOCYST DIVISION• SOMATIC CELL NUCLEAR TRANSFER
  27. 27. Blastocyst Division• Fertilized cell allowed to divide till mass is 30- 150 cells (Blastocyst)• Split Blastocyte into two• Each half implanted in a surrogate mother• Creation of identical twins
  28. 28. HOW SCIENTISTS CLONE CELLS…• BLASTOMERE SEPARATION• BLASTOCYST DIVISION• SOMATIC CELL NUCLEAR TRANSFER
  29. 29. Somatic Cell Nuclear Transfer (Overview)• Use cells of only ONE parent• Somatic Cell (any body cell EXCEPT an egg or a sperm)• Enucleated Egg Cell (egg with its nucleus removed)• Merge both cells via fusion• Only applicable on immature cells (either embryonic, or of young animals)
  30. 30. Somatic Cell Nuclear Transfer (Breakthrough- Birth of Dolly)• In 1996, by improved somatic cell nuclear transfer method• Donor cell made quiescent (less active)• Transfer of genetic material from udder cell to an enucleated cell (from a second sheep)• Resulting embryo was implanted into the uterus of a third sheep• Now donor cells can be taken from adult animals
  31. 31. Egg Donor
  32. 32. Genetic Donor
  33. 33. Enucleated Cell
  34. 34. Embryo Development
  35. 35. Embryo Implantation
  36. 36. Birth
  37. 37. Somatic Cell Nuclear Transfer (Glitches)• All genes are NOT in nucleus, so all genes of the clone are NOT those of the donor• Since every organism is influenced by, both genes and the environment, so the clone’s life will be different from that of the parent
  38. 38. STEM CELLS AND CLONING
  39. 39. Basics• At Blastocyte stage, embryonic cells can divide into ALL types of cells needed by the organism• Scientists separate these cells and coax them to divide under special conditions (so that they can form any cell type)• Humans maintain some stem cells in some tissue of body till death. But with aging, they lose ability to transform into different cell types (cells from bone marrow is exception)
  40. 40. Benefits• Can be used to cure diseases• If a patient receives stem cells cloned containing his own genetic material, then his/ her immune system would not reject them as foreign material• Research going on to find cure for Parkinson’s, paralysis, damaged heart muscles, arthritis and diabetes mellitus
  41. 41. Results• Still in experimental stage• First clinical trial of curing patients suffering from Parkinson’s produced mixed results  Patients over 60 years old reported no improvement  Younger patients reported some improvement, but 15% of them sport irreversible side effects, like uncontrollable twitching
  42. 42. Risks• If some error occurred during cloning, then all resulting cells will have same error• However, in 2002, scientists at Rutgers University found comparatively fewer genetic mutations• Risk of transferring disease via stem cells  Typically, scientists culture human stem cells with mouse cells  Mouse cells have some unknown nutrient that keeps human stem cells alive  So human cells can easily be infected by mouse cells
  43. 43. BenefitsofCloning
  44. 44. Benefits of Animal Cloning• In Agriculture  Cloned cattle could produce higher yield of milk & meat  Can also produce drugs at commercial level• In Laboratory  Create animals with human diseases  Can test cures on them safely
  45. 45. Cloning Endangered & Extinct Species• 2001- Gaur (endangered ox of South-East Asia) cloned successfully• Plan to revive extinct species by cloning  Cells of last Spanish ibex (mountain goat) preserved for the same purpose• Prerequisites  Cell with intact nucleus  Surrogate mother needed with similar genetic makeup, to implant the embryo
  46. 46. Can Humans Be Cloned…….?• Impossible up till now• In human embryo, number of cells become twice after every 24 hours  Not achieved yet in laboratory• Not enough funding due to its controversial nature
  47. 47. Controversies• People do not consider plant cloning as cloning: Main opposition is against animal cloning• Arguments:  Man should not play God Will increase social gaps, as babies with special traits, like beauty, athleticism, or intelligence can be created

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