1. Textbook Reference: pg. 38-45

2.  Mitosis produces cells with exact copies of the same chromosomes…therefore the same genes  But cells will produce different proteins and therefore differ in structure and function  E.g. Bone cells, nerve cells, muscle cells, skin cells….

3.  Every new organism (animal or plant) begins as a single cell, the fusion of their parents genes (sperm + egg = zygote)  This cell divides into two identical cells by the processes of mitosis and cytokinesis.  Two daughter cells then divide and the process continues.

4. Blastocyst

5.  Every cell contains the same chromosomes and the same genes.  How then do organisms produce very different types of cells?

6.  Not every gene in a cell gets expressed or “switched on”.  Therefore, not every protein gets produced!

7.  What decides how/which genes are expressed? 1. Cytoplasm in the Cell – amount of cytoplasm and number of other organelles affects how the cell will develop 2. Environmental Conditions of the Cell – temperature, nutrients, contaminants…. 3. Neighbouring Cells – diffusion across the cell membranes from one cell to another when cells are close to each other (chemical communication between cells)

8.  Both plants and animals have cells which can become ANY type of cell  Plants – meristematic cells  Animals – embryonic stem cells

9. ANIMALS - STEM CELLS  Unspecialized cells – the first few cells within an embryo are totipotent - able to eventually become any type of cell  As an embryo develops (after 1 week), cells become less versatile and can only produce some kinds of cell (tissue). They are pluripotent.  After birth, people have only adult stem cells (or unipotent)– these can only produce very specific types of cell. E.g. Skin cells can only produce more skin cells.

11.  Embryonic stem cells – can be cultured (grown) to produce many types of tissue  Holds great promise for treating many diseases including life-threatening ones. Many would say that this fact alone should mean “full speed ahead” with research.

14.  Requires the destruction of an embryo - usually grown from eggs fertilized with sperm “in vitro” (outside the womb)  Some say this is destroying a human life (a person)  Some say that personhood does not come until much later (brain cells?, blood?)

15.  Adult stem cells – can be cultured (grown) to produce the type of tissue they came from  No ethical issue  Requires the addition of “growth factors” (nutrients)

16.  Embryos can only be used which are no longer wanted for reproductive purposes.  Illegal to “create” embryos solely for stem cell research  Embryos must be less than 14 days old (after conception) to be used to harvest stem cells  Donors must provide consent to the use of embryos  Cannot buy/sell embryos

17.  Very recent research (last 5 years)  Taking normal tissue cells (e.g. skin) that are unipotent and “forcing” them to become pluripotent (by the addition of genes)  A kind of “cellular reprogramming”  This removes the ethical issue (no destruction of embryos/blastocysts)

18. http://singularityhub.com/2009/06/08/growing-organs-in-the-lab/

19. Human skin grown in the lab from stem cells

20.  http://www.youtube.com/watch?v=4nqw1yjyK Es&safety_mode=true&persist_safety_mode=1 &safe=active http://www.youtube.com/watch?v=4nqw1yjyK Es&safety_mode=true&persist_safety_mode=1 &safe=active