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CLONING

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CLONING

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    1. CLONING Anne Simpson, Jan ‘03

    2. “Who can quantify the indescribable source of emotion pleasurable and otherwise that children engender in their biological and social parents? It is this above all else which drives individuals to take extreme measures to achieve or avoid parenting in the modern world.” Infertility in the Modern World; Present and Future Prospects, GR Bentley

    3. “Why should another child die from leukemia when if the technology is allowed we should be able to cure it in a few years time?” Simon Smith, The Human Cloning Foundation

    4. Background First reproductive cloning in 1952 in Amphibia.   First mammal cloned in 1996 in Edinburgh -Dolly the sheep. Sheep, cattle (1998), mice (1998), goats (1999) and pigs (2000) have all been cloned.

    5. What is cloning? Embryo Splitting or “Cloning” Somatic Cell Nuclear Transfer (SCNT) Reproductive Cloning Therapeutic Cloning

    6. Embryo splitting or “cloning” Separation of human embryo into 2 parts. Cells removed from fertilised ovum - have the potential to develop into a blastocyte If implanted can develop into a child. Genetically identical monozygotic twins The embryo can be spilt only a limited number of times, and a “clone’ is not produced.

    7. Somatic Cell Nuclear Transfer Nuclear material removed from donor egg DNA inserted into the enucleated egg Reconstituted zygote formed, equivalent to a fertilised ovum. Potential to divide into a blastocyte If implanted, develops into child genetically identical to the nuclear donor - Reproductive cloning. In reproductive cloning the clone would be the identical twin of the donor

    8. Schematic representation of Somatic Cell Nuclear Transfer

    9. Therapeutic cloning SCNT Blastocyte (embryo) cultured to produce an embryonic stem cell line Excludes most blastocyte cells, effectively destroying the embryo Undifferentiated embryonic stem (ES) cells can then be made to differentiate into precursor cells.

    10. Stem Cells A stem cell is defined as: A cell that can proliferate indefinitely and differentiate into a wide variety of cell types Adult stem cells are found in bone marrow, isolated and encouraged to proliferate Nuclear reprogramming – obtain ES cells by directly dedifferentiating normal body cells in vitro

    11. “Few issues linked to genetic research have raised as much controversial debate as the use of somatic cell nuclear transfer technology (SCNT) to create embryos specifically for stem cell research” The Pros and Cons of Human Therapeutic Cloning in the Public Debate, Journal of Biotechnology, Sep 2002

    12. Benefits of Therapeutic Cloning Therapeutic cloning has the potential significantly to reduce human suffering and enhance human happiness. In it may lie the potential to overcome tissue rejection and the opportunity to increase understanding of cellular development  

    13. Ways in which cloning may be expected to benefit mankind: Use of embryonic stem cells to treat degenerative and autoimmune conditions such as Alzheimer’s Disease, Parkinson’s Disease, diabetes, heart failure, arthritis etc. and to treat burns victims and spinal cord injuries. Infertility treatment Plastic, reconstructive and cosmetic surgery Leukaemia and other cancers Transplants – Kidney and liver

    14. The Scientific and Ethical Debate Therapeutic cloning involves deliberate production of cloned human embryos so that through their destruction patients may receive treatment. Majority of scientific opinion opposed to the reproductive cloning of humans in view of the developmental, morphological and physiological problems observed in mammals that have been cloned

    15. Ethical Questions Two questionable procedures – cloning of humans destruction of human embryos Main ethical arguments against therapeutic cloning centre on the moral status of the human embryo Most ethical questions concerning status of the human embryo been examined in the context of abortion

    16. Reproductive cloning- Low efficiency Low efficiency of reconstituted eggs developing to parturition. 1 cloned animal to parturition, approx. 100 eggs must be enucleated and reconstituted i.e. only 1% efficient Weak argument when considered that IVF requires harvesting of up to 40 eggs

    17. Reproductive cloning -Abnormalities risk Developmental abnormalities - large offspring syndrome – oversized offspring with disproportionately sized organs, respiratory and circulatory problems, May not be a risk in humans Incidence of congenital abnormalities in animals is as high as 35%. Developmental abnormality following natural sexual reproduction is 3%

    18. Reproductive Cloning - Genetic Engineering Cloning makes it easier to meddle with genes, another form of genetic engineering Risk of incompletely reprogrammed genes, could be minimised by the optimum culture conditions used in IVF.

    19. Therapeutic Cloning – Adult stem cells Many benefits of embryonic stem cells can be achieved using adult stem cells. Adult stem cells are demonstrating greater multipotency than expected Adult stem cells hard to isolate and have restricted proliferation potential. Range of cells they can be differentiated into is limited Risks of using blood stem cells from a cancer patient’s own bone marrow to restore their immune system – some might be cancerous

    20. Therapeutic Cloning Cloned cells may be more vigorous and therefore at greater risk of becoming cancerous Studies using cloned blood stem cells in cows came from 100-day old fetuses

    21. Embryo status Are embryos already human beings? Society still divided over how to regard the moral rights of and its duties towards the human embryo. Are human embryos entitled to protection from intentional destruction.

    22. Ethical Dilemma Relief of suffering is not a sufficient argument to justify the means. Abortion legislation in most countries suggests the rights and choice of grown adults supercede the rights of the early embryo

    23. “If the position were taken that embryos are not persons and may be destroyed, and that position turns out to be wrong, we will have endorsed the killing of thousands if not millions of human beings. If human embryos however are not persons, but we treat them as is they were the potential harm is that therapies might become available more slowly.” What to call Human Cloning O’Mathuna, European Molecular Biology Organisation

    24. Middle Ground Bioethicists recommend aggressively pursuing adult stem cell research while upholding the highest ethical standards for medical research

    25. Current International Regulations US expected to ban reproductive cloning, still debating whether to allow therapeutic cloning Australia recently passed bill allowing harvesting of stem cells from surplus IVF embryos. Reproductive and therapeutic cloning have been banned

    26. Current International Regulations cont. European countries - unanimous prohibition reproductive cloning No agreement on permission for research into therapeutic cloning. UK took the lead and voted in favour of regulations allowing therapeutic cloning UK law allows researchers to harvest stem cells from surplus IVF embryos and conduct therapeutic cloning

    27. Human Fertilisation and Embryology Act 1990 “…to make provision in connection with human embryos; to prohibit certain practices in connection with embryos and gametes; to establish a Human Fertilisation and Embryology Authority…”

    28. Human Fertilisation and Embryology Authority   “A statutory body which regulates licenses and collects data on fertility treatments such as IVF and donor insemination as well as human embryo research in the UK”. Set up in 1991

    29. Human Fertilisation and Embryology Authority Ensure high national standards, monitors all research, supervises controlled research, considers ethical implications in light of the national debate 21 members appointed by UK Health Ministers based on personal knowledge and expertise, half of whom come from disciplines other than medicine or human embryo research

    30. References Cloned stem cells may give new lease of life New Scientist What to call Human Cloning O’Mathuna, European Molecular Biology Organisation Reiss MJ, Ethical Dimensions of Therapeutic Human Cloning, Journal of Biotechnology, Sep 2002 The Pros and Cons of Human Therapeutic Cloning in the Public Debate Journal of Biotechnology, Sep 2002 Infertility in the Modern World; Present and Future Prospects, GR Bentley The Human Cloning Foundation www.howstuffworks.com Commentary on Human Cloning Byrne & Gurdon, Differentiation 2002 www.hfea.gov.uk www.newscientist.com

    31. INFERTILITY Management of Infertility Clinical Review 2002, BMJ BMJ 2002;325:28-32 (6July) The Initial Investigation and Management of the Infertile Couple RCOG, Evidence Based Clinical Guidelines,1998 www.rcog.org.uk/guidelines

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