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Ch. 16   Human intervention in evolution
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Ch. 16 Human intervention in evolution


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  • 1. Human Intervention in Evolution
  • 2. Advantages of Artificial Selection
    Specific individuals selected to contribute to next generation for:
    Economic reasons
    Aesthetic reasons
  • 3. Reproductive Technologies
    Artificial insemination
    Multiple ovulations and embryo transfer (MOET)
    Sex selection through sperm sorting
    Oestrus synchronisation
  • 4. Artificial Insemination
    Semen is collected from male and transferred to females
    Advantage is yield: normally in a single mating there is the potential for one female to be inseminated
    Via artificial insemination one ejaculate can fertilise 10 females.
    Semen can be snap frozen in liquid nitrogen and stored for many years
  • 5. Artificial Insemination
    Can fertilize many females
    Can fertilize distant females
    Can fertilize beyond the lifespan of the male
    Prized male can make larger genetic contribution
    Loss of genetic diversity
    As one allele is favoured, alternatives are completely lost
    Whilst breeding for a particular trait, others may be unintentionally gained or lost
  • 6. Artificial Insemination in plants
    Cover stigma
    Remove stamen
    Collect pollen from anthers
    Expose to stigma of many other plants
  • 7. Artificial Insemination in plants
    When one species is used to fertilize another, a hybrid is produced
    As chromosomes are non-homologous, hybrid is sterile
    Treatment with certain chemicals will cause doubling of chromosomes in all cells, thereby producing a fertile hybrid
    Sterile hybrid
    Treatment with colchicine
    Fertile hybrid
  • 8. Multiple ovulations and embryo transfer (MOET)
    Valued females can also make a larger genetic contribution.
    Inject with FSH (stimulates super-ovulation)
    Inject with GnRH (all eggs mature simultaneously)
    Fertilise eggs through in-vitro fertilisation
    Implant eggs in to surrogate female
    MOET will usually increase the yield of a valued female by a factor of 7
  • 9. Sex selection through sperm sorting
    Add a harmless fluorescent dye to sperm
    Dye attaches to DNA
    X chromosomes contain more DNA
    Sperm containing X chromosome will fluoresce more brightly
    Select these sperm
  • 10. Oestrus synchronisation
    All females in herd are effectively “put on the pill” by being given progesterone.
    If all are taken of progesterone at the same time, ovulation will occur simultaneously.
    Makes herd easier to manage
  • 11. Cloning
    Technique #1 – Embryo splitting
    Pryor to blastocyst formation (>32 cells), the cells of the zygote can be divided with a very fine needle and implanted in to a surrogate.
    Technique # 2 – Nuclear transfer
    Can be performed via somatic cell fusion
    Can be performed via fusion with a donor embryo cell
  • 12. Somatic cell fusion
    Fusion with a donor embryo
  • 13. Dolly was created via nuclear transfer (somatic cell fusion)
  • 14. Some cloning successes
    Snuppy with the “mother” from which she was cloned
    Snuppy with her surrogate mother
  • 15. The downside to cloning
    Many unsuccessful attempts
    CC (cat): 87
    Snuppy (dog): 123
    2nd Chance (bull): 189
    Dolly (sheep): 277
    This does not apply to plants as cloning occurs naturally
    (cuttings, runners, rhizomes)
    Shortening telomeres
    Every time a cell divides it loses some DNA from its telomeres (ends of the chromosomes)
    Implies that clones are born with “old” DNA
    Recent studies have indicated that this may not be the case
    Clones had loner telomeres than original
  • 16. Transferring genes
    A gene transferred to bacteria is transformed
    eg. human insulin grown in bacterial colony
    A gene transferred to another species is transfected
    eg. Spider gene in goat allows silk to be harvested from goat’s milk
    Gene therapy involves the replacement of a faulty allele with a working one
  • 17. Stem Cells
    The source of the stem cell will determine how far-reaching its adaptive abilities are.
  • 18. Harvesting Stem Cells
    Pluripotent stem cells are taken from the inner cell mass of a blastocyst.
    Stem cells can be used to replace damaged or diseased cells in almost any part of the body
  • 19. Therapeutic (non-reproductive) cloning
    Embryos can also be cloned from the healthy cells of a diseased patient to create stem cells of the appropriate blood and tissue type.
  • 20. Ethical Issues
    Extraction of stem cells destroy what may have been a perfectly healthy embryo.
    Current legislation states that stem cells may only be taken from embryos deemed to be “in excess” during IVF procedures.
    Embryos cannot be created simply for the purpose of harvesting stem cells
  • 21. Overcoming Infertility
    Infertility problems are usually 50% female, 30-40% male and 10-20% incompatibility.
    Donor Sperm
    Legally the child belongs to the mother and her husband at the time of birth
  • 22. Overcoming Infertility
    IVF (In-vitro fertilisation)
    Low sperm count
    Poor swimmers
    Damaged fallopian tubes
    Hostile mucous
    Problems associated with implantation of egg in to uterine wall
  • 23. In-vitro fertilisation
    Egg incubated with sperm in culture fluid
    Protective band of cells removed from around fertilized egg
    Embryo returned to mother’s uterus at either the 2 or 4 cell stage
  • 24. Overcoming Infertility
    IVF with donor egg
    Implant IVF fertilised egg in to the womb of another female
    GIFT (gamete intrafallopian transfer)
    Sperm and eggs unable to meet can be collected and placed together in the fallopian tube
    Intracytoplasmic sperm injection
    Sperm unable to naturally penetrate egg are injected
  • 25. In Conclusion
    IVF ethical issues:
    What happens to frozen egg, sperm or embryos after the death of one parent?
    On request of the family, can sperm / eggs be collected from someone after an untimely death?
    Chapter review questions:
    Ch. 16: 3-5,7,8,11