1. Stem Cells Where we find them, and how they can be used in medicine.

2. Specification 11 Explain what is meant by the terms stem cell, pluripotency and totipotency and discuss the way society uses scientific knowledge to make decisions about the use of stem cells in medical therapies (e.g. regulatory authorities relating to human embryo research, ability of stem cells to develop into specialised tissues, potential sources of stem cells, who could benefit from the therapies, procedures to obtain stem cells and their risks). 12 Describe how totipotency can be demonstrated practically using plant tissue culture techniques.

3. What is a stem cell? A stem cell is a cell that is able to replicate itself while maintaining an undifferentiated state, and is then able to differentiate into mature cell types. In humans; there are three types of basic stem cell. They range from completely undifferentiated to partly differentiated. Totipotent stem cells-zygote- undifferentiated Pluripotent stem cells- Embryonic stem cells- (almost completely) undifferentiated Multipotent stem cells- Adult stem cells- partly differentiated http://www.sumanasinc.com/webcontent/animations/content/ stemcells.html

4. Type of stem cell DefinitionWhere are these cells found? How many are there? totipotent are undifferentiated cells which can divide and give rise to all the cell types in an organism. They are the first eight cells in an embryo. pluripotent Are undifferentiated cells (have begun to differentiate a tiny bit) which able to give rise to most, but not all cell types in an organism. They are the inner mass (50 cells) of the blastocyst stage of an embryo. multipotent are differentiated cells which retain the ability to give rise to a limited amount of different cell types. In adults, for example, white blood cells in the bone marrow can give rise to range of different types of blood cells. Activity 3.12a Stem Cells Reference for blastocyst picture: http://www.daviddarling.info/encyclopedia/B/blastocyst.html

6. QUESTIONS for a Quiz 1.Where can you find multipotent cells? 2.Where can you find pluripotent cells? 3.Where can you find totipotent cells? 4.What type of stem cell is differentiated and can only become a few other cells? 5.Which type of stem cell can become an entire organism? 6.Which type of stem cell can become most of the cell types in an organism?

7. Use of Stem Cells in Medicine and Research How can stem cells be used for research? Help understand how cancer cells form Investigate certain birth defects Help undertand how genes trigger organ development How can stem cells be used in medicine? Provide universal new donor cells, tissues or organs for treatment by transplantation. Which stem cells are most often used for medicine and research? Embryonic stem cells –pluripotent stem cells

8. Type of Stem Cell Source of the Stem Cells Stem Cell Potential Use in Medicine Ethical Considerations Embryonic - Totipotent After zygote has gone through 3 cycles of division, it consists of 8 identical cells. Each cell can develop into a complete human being. Do not reproduce after 8 cells. Cannot be kept in lab as cell culture. Not used often. Embryonic - Pluripotent Inner cell mass of the blastocyst (50 cells that would usually form embryo). Spare embryos from in vitro fertilsation clinics. Can develop intp most cell types but not an entire human being. Develop tissues for transplantation. (Possible IS rejection) See table on next page. Adult – Mulitpotent Neural stem cells from CNS. Blood stem cells from bone marrow. Cells have become differentiated. Neural stem cells become different neurones Limited. Less valuable for reaserch because differentiated. No ethical considerations.

9. Spare embryos from IVF are cultured to the blastocyst stage. The stem cells are removed and the embryo discarded. The stem cells are used in research to see if tissues for transplant could be created. Problems? If the right type of tissue is developed, there may still be issues with rejection by the body’s immune system. How can this problem be overcome? This may be overcome by tissue typing (20 stem cell lines for 90% population) or use of drugs to avoid rejection. Theraputic cloning http://www.wwnorton.com/college/biology/discoverbio3/core/content/ch15 /animations.asp http://www.wwnorton.com/college/biology/discoverbio3/core/content/ch15 /animations.asp How can pluripotent cells be used to provide new cells, tissues and organs?

10. Therapeutic Cloning http://www.barglow.com/cloning-1.gif Diploid nucleus is removed from patient needing transplant Ovum has haploid nucleus removed Diploid nucleus fused with ovum using electric shock (somatic cell nuclear transfer) This cell is then stimulated to divide by mitosis. After 5 days there should be a blastocyst Stem cells are then isoltaed from blastocyst and used to create tissues that are genetically identical to patient

11. This research has been allowed by the government, but all embryos must be destroyed after 14 days, to avoid human cloning.

12. Type of cellHow obtained or how produced Potential medical benefits Legal or ethical issues Pluripotent human stem cells Therapeutic cloning (somatic cell nuclear transfer) (Human and animal- human) Mutipotent adult stem cells Isolated from ‘spare embryos’ from IVF treatment (50 inner cells removed from blastocyst) Used to develop tissues/organs for transplantation Problem: Immune sytem rejection Drugs to suppress immune system Use tissue typing to match to patient’s tissue Legal to use surplus embryos form IVF treatment Ethical issues: see handout. Remove patient’s diploid cell nucleus Insert into ovum with no nucleus Mitosis happens and a blastocyst forms 50 inner cells removed to produce tissues that are genetically identical to patient No rejection by the immune system because tissues are genetically identical Legal for therapy only Ethical issues: see handout (not all arguments can be used)

13. Who would benefit from stem cell research? Parkinson’s disease: Replace faulty brain cells Diabetes: Replace insulin producing tissue in the pancreas Damaged nerves: Replace spinal nerves so that limbs can work again. Heart damage from a heart attack: Repair damage with new heart muscle Organs for transplant: Replace organs that no longer work, such as livers, kidneys, hearts etc.

14. AGAINST: Embryonic stem cells are (potential) people/babies from the moment of conception Objectional on religious grounds Pressure on women to produce surplus embryos Cloning/stem cell techniques may get into the wrong hands/regulation might be difficult to police It will soon be possible to use non-embryonic stem cells so research into the use of embryonic stein cells is unnecessary Although there are some advantages there could be unexpected dangerous consequences therefore not worth the risk FOR: Potential for alleviating human suffering e.g. culturing patient’s own cells to provide replacement tissues/organs Stem cells from IVF would otherwise be discarded; Embryos should not be considered as human at an early stage (from blastocyst stage) More can be done with embryonic stem cells than differentiated adult stem cells; Ethically questionable to use embryonic stem cells but these objections are outweighed by the greater evil of not using embryonic stem cells to alleviate human suffering Could be excesses but these can be regulated Ethical Considerations of using Embryonic Stem Cells

15. Regulatory Authorities What are regulatory authorities? – HFEA What are their roles? – Promote advances in the treatment of infertility – Increase knowledge of congenital diseases – Increase knowledge about the causes of miscarriage – Develop more effective methods of contraception – Develop methods of detectinh genetic abnormalities in embryos before implantation

16. Do plants have stem cells? Yes, actually most plant cells remain totipotent throughout the life of a plant Plant cells can dedifferentiate e.g. a root hair cell can change into a palisade cell exposed to the correct chemical signals. Therefore you can grow a whole new plant from a root, stem, leaf. Plants can be reproduced by using plant tissue culture (micropropagation) Plants and Stem Cells

17. Micropropagation produces many plants which are genetically identical (clones) Plants and Plant Tissue Culture- Micropropagation

18. Plants and Plant Tissue Culture (Micropropagation) Micropropagation producing many plants which are genetically identical (clones) Put the following steps in order a)The callus grows into an embryonic plant b)Place explants on a solid agar medium which will contain nutrients and growth regulators c)Surface sterilise the explants to remove bacteria and fungi, and thus avoid the plant growing poorly or death d)Embryos form into genetically identical clones e)Remove small pieces of plant to be cloned – these are called explants f)The cells divide by mitosis to form a mass of undifferentiated cells known as a callus Answer: 1)e, 2)c, 3)b, 4)f, 5)a, 6)d

19. Plant Tissue Culture - Micropropagation Remove small pieces of plant to be cloned – these are called explants. Surface sterilise the explants to remove bacteria and fungi, and thus avoid the plant growing poorly or death. Place explants on a solid agar medium which will contain nutrients and growth regulators. The cells divide by mitosis to form a mass of undifferentiated cells known as a callus. The callus grows into an embryonic plant. Embryos form into genetically identical clones.

20. Why is plant tissue culture important? Plant biology research Plant breeding Genetic modification of plants Conservation of endangered plants