Therapeutic cloning


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Introduction and description of therapeutic cloning along its applications and ethical issues.

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Therapeutic cloning

  1. 1. Cloning  It is a process for making numerous copies of organisms or cells or of individual genes which are genetically identical.  It refers to the transfer of somatic cell’s nucleus into an ovum, which then grows into an embryo
  2. 2. History  1952 Thomas J. King and Robert Briggs Northern leopard frogs  1962: John Gurdon South African frogs
  3. 3. Early Frog Experiments (gurdon’s Method)  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
  4. 4. 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
  5. 5.  1964: F.C. Steward cloned Carrot  1969: First gene isolation  1972: First recombinant DNA molecule  1977: Mouse  1983: Nuclear transfer
  6. 6.  1984: Steen Willadsen Cloned a sheep from embryo cells  1986: Nucleus of an adult cell can also be used  1996: Ian Wilmut Villainous sheep "Dolly"
  7. 7. Types of Cloning  Cloning is of three types which are as follows (1) Recombinant DNA technology or DNA cloning (2) Reproductive cloning (3) Therapeutc cloning
  8. 8. Recombinant DNA technology or DNA cloning  DNA cloning, Molecular cloning, Gene cloning  The production of exact copies (clones) of a particular gene or DNA sequence using genetic engineering techniques.
  9. 9. Reproductive Cloning  Technology to produce a genetically identical organism or an animal with the same nuclear DNA as an existing, or even an extinct, animal.  An embryo is produced through the removal and transfer of nuclear material in a cell, and the use of a growth medium to manipulate that cell into undergoing mitosis.
  10. 10.  Cloning animals for research  Cloning endangered species In order to expand population  Cloning extinct species To research their behavior and other characteristics
  11. 11. Sheep Goats Cows Mice Pigs Cats Rabbits gaur
  12. 12. Therapeutic Cloning  Embryo cloning  Nuclear transplantation of a patient’s own cells to make an oocyte from which immune- compatible cells (especially stem cells) can be derived for transplant.  Not cloned humans or animals  Stem cells harvested at the stage of blastocyst
  13. 13. How is Therapeutic Cloning Performed? Somatic Cell Nuclear Transfer Somatic cell Nuclear Transfer
  14. 14. SCNT Process (1) Remove the nucleus from an unfertilized egg cell (A). (Done under a microscope.) Suction pipette (B) Glass needle (C)
  15. 15. SCNT Process (2) Gently push the glass needle through the tough shell that surrounds the egg cell.
  16. 16. SCNT process (3) The egg cell’s nucleus (A) has been released outside of the egg. What remains is an “enucleated” egg (B).
  17. 17. SCNT process (4) •Inject the nucleus (at arrow) from a donor cell into the enucleated egg cell. • Ease the tip of the glass needle deep into the enucleated egg cell. Then, deposit the donor nucleus.
  18. 18. SCNT process (5)  After completing the nuclear transfer, the unfertilized egg cell is “activated” using a chemical or electrical treatment that stimulates cellular division.
  19. 19. SCNT process (6)  The proliferating cells form a structure called a blastocyst within days. It is roughly the same size as the egg cell. The right-hand image shows the blastocyst “hatching”
  20. 20. Difference B/W Fertilization & SCNT Fertilization = two set of chromosomes one from sperm and one from egg SCNT = two set of chromosomes both from somatic cell as egg’s nucleus has been removed
  21. 21. 3 goals of therapeutic cloning by SCNT in humans  Use embryo as source for ES cells  Use ES cells to generate an organ  In this case the organ generated will carry cells with the same genetic markers as the patient (recipient)  Correct genetic error in ESC in blastula stage
  22. 22. What Are Stem Cells? Stem cells are the raw material from which all of the body’s mature, differentiated cells are made. Stem cells give rise to brain cells, nerve cells, heart cells, pancreatic cells, etc.
  23. 23. Special characteristics of ALL stem cells  Self-renewal (proliferation)- the ability of a stem cell to clone itself indefinitely by cell division.  Relocation and Differentiation are abilities of stem cells to “migrate” to where they’re needed in the body and specialize into a particular type of mature cell
  24. 24. What’s so special about Stem Cells?  They have the potential to replace cell tissue that has been damaged or destroyed by severe illnesses.  They can replicate themselves over and over for a very long time.  Understanding how stem cells develop into healthy and diseased cells will assist the search for cures.
  25. 25. Two Kinds of Stem Cells  Embryonic (also called “pluripotent”) stem cells (ESC) are capable of developing into all the cell types of the body.  Adult stem cells are less versatile and more difficult to identify, isolate, and purify. Stem cells have been found in the blood, bone marrow, liver, kidney, cornea, dental pulp, umbilical cord, brain, skin, muscle, salivary gland .
  26. 26. Embryonic development
  27. 27. ESCs are pluripotent They retain the ability to develop into nearly any cell type
  28. 28. Benefits of Therapeutic cloning  Organ transplant alternative  Leukemia  Degenerative Diseases  Spinal cord repair  Skin grafts
  29. 29. Organ Transplant
  30. 30. Pitfalls of therapeutic cloning Practical and Technical Issues Ethical Issues
  31. 31. Practical Issues  Some immune rejection may occur- WHY?  About 1% of the DNA in the clone will NOT be identical to donor cell (patient)  It will be identical to egg cell used in SCNT  REASON: mitochonrial DNA in eggs  Human mitochondria carry about 13 genes, some of which code for surface proteins
  32. 32.  Large number of eggs needed for SCNT  To harvest large number of eggs:  Excessive hormone treatment of females  Surgery to retrieve eggs  Both can be harmful to female human  Cow/pig females may be used  Cow/pig eggs will carry species-specific mitochondrial genes  Steadiness of stem cells
  33. 33. Ethical issues  Religion  Law  Moral values  Destruction of Embryo  Killing of life