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STEM CELLS AND CLONING

STEM CELLS AND CLONING

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STEM CELLS AND CLONING

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  1. STEM CELLS AND CLONING

  2. Stem Cells • Characteristics • They continue to grow and proliferate, • Given the correct signals (from a hormone or a ‘growth factor’) they can differentiate into a particular specialized cell type • Stem cell video (7 min)

  3. Some stem cells have more abilities than others • A totipotent stem cell can form not only adult cell types, but also the specialized tissues needed for development • EX: Zygote

  4. A pluripotentstem cell can form most or all of the 210 differentiated cell types in the adult body EX: Inner Cell mass of blastocyst

  5. A multipotentstem cell can form only a few differentiated cell types EX: Umbilical Cord blood Bone marrow

  6. Where do we get stem cells? • Sources of stem cells • Early embryos from fertility clinics • Somatic cell nuclear transfer • Tissue-based (adult) stem cells- Skin, Sperm, Fat, Bone • Ethical issues associated with use of embryos • Stem cell video

  7. Embryonic Stem Cells • Hope- Regenerative medicine • A lot of cells can be grown and then given hormonal signals to specialize into a specific tissue • This could be used to create new cells or tissue on demand and treat illnesses such as diabetes, Alzheimer’s and spinal cord injuries

  8. Embryonic Stem Cells • Problems • Inefficient to get them to start growing and keep growing in the laboratory • Hard to form the desired specific cell type in the culture dish. • Could form tumors in patients • Only scant evidence that embryonic stem cells can actually work in the body

  9. Differentiation of embryonic stem cells in culture Liver cells Culturedembryonicstem cells Nerve cells Heart muscle cells Different cultureconditions Different types ofdifferentiated cells Figure 11.5

  10. Stem Cells Donorcell Nucleus fromdonor cell Implant blastocystin surrogate mother Clone of donoris born(REPRODUCTIVEcloning) Removenucleusfrom eggcell Add somaticcell fromadult donor Grow in culture to producean early embryo (blastocyst) Remove embryonic stem cells from blastocyst andgrow in culture Induce stemcells to formspecialized cellsfor THERAPEUTICuse

  11. Figure 2.24

  12. Cloning • Cloning means to make an identical copy of something, including copying DNA • Cloning a new organism from a pre-existing one is known as asexual reproduction because it does not involve sex

  13. How to Clone Tadpole (frog larva) Frog egg cell Nucleus UV Intestinal cell Nucleus Transplantationof nucleus Nucleusdestroyed Tadpole Eight-cellembryo

  14. Micropipette about to penetrate unfertilized sheep egg to remove nucleus Egg has been emptied of its nucleus, which holds DNA DNA from donor cell is about to enter the enucleated egg. A spark will stimulate cell divisions.

  15. Dolly, the first cloned sheep, with her lamb