Successfully reported this slideshow.
We use your LinkedIn profile and activity data to personalize ads and to show you more relevant ads. You can change your ad preferences anytime.

Animal cloning

6,880 views

Published on

Published in: Technology, Spiritual
  • Be the first to comment

Animal cloning

  1. 1. ANIMAL CLONINGBLS 308/209HOZA, A.SMAY, 2009<br />
  2. 2. Types of cloning<br />• Recombinant DNA cloning<br />• Therapeutic cloning<br />– Stem cells<br />• Reproductive cloning<br />– Embryo splitting<br />– Somatic cell nuclear transfer (SCNT)<br />
  3. 3. History of cloning by SCNT<br />• Nuclear transfer was performed with frogs in the 1950s<br />• Cattle were cloned by transfer of embryonic nuclei in the 1980s<br />• Dolly was the first animal cloned by SCNT from an adult cell in 1997<br />
  4. 4. Animals cloned by SCNT<br />• Sheep, pig, goat, cattle, cat, rabbit, mouse, mule, horse, rat, deer, fish<br />• Cloning efficiency for Dolly, 1/277 reconstructed embryos (0.3%)<br />
  5. 5. Basic SCNT Methodology<br />Injection of donor cell under the ZonaPellucida<br />Injection of donor cell or Isolated nucleus into The cytoplasm<br />
  6. 6. SCNT-chromatin transfer<br />• Chromatin condensation<br />• Fusion with an enucleated egg<br />• Enhanced survival of clones<br />
  7. 7. Challenges to successful SCNT<br />• Reprogram a nucleus from a differentiated stage (somatic cell) to an embryonic stage<br />• Properly activate genes necessary for early embryonic development and suppress differentiation associated genes<br />
  8. 8. Pet cloning<br />• Dog cloning- MissiplicityProject<br />• Cat cloning<br />Shin et al., 2002<br />
  9. 9. Clones of clones<br />• Mice have been serially cloned to 6 generations<br />• Cattle have been serially cloned to 2 generations (3rd generation failed)<br />Donor<br />clone 1<br />clone 2<br />Kubota et al, 2004<br />
  10. 10. Literature survey of developmental problems in cloned animals<br />77% of cloned<br />Animals are<br />healthy<br />Cibelli, 2002<br />
  11. 11. Embryonic problems with SCNT<br />• High mortality during gestation<br />• >65% of one cell cloned embryos fail to develop to morula/blastocyst<br />• Days 30-60<br />– Cloned cattle: 50-100% embryonic loss<br />– Normal service: 2-10% loss<br />– In vitro fertilization: 16% loss<br />• Increased incidence of spontaneous abortions during second trimester<br />• Abnormal placentas<br />
  12. 12. Postnatal problems with SCNT<br />• Abnormally high birth weight<br />• Respiratory and metabolic abnormalities<br />– Lung dysmaturity<br />– Pulmonary hypertension<br />• “Adult clone sudden death syndrome” -<br />cloned pigs died of heart failure at less than6 months <br />
  13. 13. Factors contributing to early embryonic death<br />• Extensive micromanipulation of oocytes and<br />somatic cells<br />– Enucleation of an oocyte, removal of 5-15% of ooplasm<br />– Electrical induced fusion<br />• Incompatibility between mitochondrial and nuclear DNA<br />• Incomplete reprogramming of somatic nucleus<br />• Immunological rejection of SCNT fetuses -<br />abnormal MHC-1 expression by trophoblast cells<br />
  14. 14. Early death of cloned mice<br />Ogonuki et al., 2002<br />
  15. 15. Abnormal expression of genes in cloned mice<br />• Global analysis of gene expression in cloned mice using DNA microarrays<br />Humphreys et al., 2002<br />
  16. 16. Cloned mice<br />• Cloned mice have an obese phenotype<br />• Phenotype is not transmitted to offspring<br />• Obesity due to epigenetic changes<br />Tamashiro et al., 2002<br />
  17. 17. Premature ageing of clones?<br />• Telomeres are specialized structures<br />at the ends of linear chromosomes that shorten with age<br />• Cloned cattle have widely varying telomere lengths<br />• Dolly’s telomeres<br />– shorter than an age-matched control<br />– consistent with a 6-year old mammary<br />cell<br /> telomere<br />
  18. 18. Advantages to SCNT<br />• Restore endangered species<br />• Allows for the targeted deletion (knockout) of genes in farm animals<br />• Alternative method for generating transgenic animals as bioreactors (pharming)<br />
  19. 19. Cloning of endangered species<br />• Gaur bull calf cloned using a domestic cow embryo and surrogate mother<br />• Cells from skin cells frozen for 8 years<br />• Clone died 48 hours after birth<br />Lanza et al., 2000<br />
  20. 20. Cloning of endangered species<br />• Cloned African wildcat<br />• Nucleus from frozen cell transferred into domestic cat oocyte<br />
  21. 21. Xenotransplantation<br />• Transfer of cells, tissues or organs between species<br />• Pigs contain alpha galactosyl sugars on the cell surface.<br />• Human and higher primate lack alpha-galactosyl sugars; thus have antibodies to alpha-gal<br />• Alpha-gal antibodies lead to acute tissue rejection<br />
  22. 22. Gene knockout technology<br />• Combine SCNT with somatic cell gene knockout technology<br />Kent-First and First, 2000<br />
  23. 23. Gene knockout in farm animals<br />• Cloned pigs lacking the alpha-galactosyltransferase gene - xenotransplantation<br />• Cloned cattle lacking prion gene <br />
  24. 24. Transgenic animal bioreactors<br />• Produce important human pharmaceutical proteins in milk<br />• Clones would provide a genetically stable line for protein production<br />
  25. 25. Advantages to cloning transgenic animals as bioreactors<br />• Increase efficiency to 100% starting with a transgenic cell line<br />• Can predetermine sex<br />• Allows for rapid expansion of genetically identical animals<br />
  26. 26. Future cloning issues<br />• Food consumption risks of cloned animals<br />– Health of animal clones<br />– Composition of meat and milk<br />• No differences in milk composition were seen between clones and control dairy cattle<br />– total solids, fat, lactose, and protein (Norman and Walsh, 2004)<br />
  27. 27. • Many different species have been cloned<br />• Animal cloning has many successes but also many complications<br />• Refinement of technique will overcome some of these problems<br />• Cloning Applications<br />– transgenesis<br />– gene knockout<br />

×