stem cells

• Stem cell - an undifferentiated cell that is capable of becoming other cell types
• cell differentiates - produces certain sub cellular structures to become a specialised cell that is adapted for its function
• sperm (23 chromosomes) + egg (23 chromosome) = zygote (46 chromosome)
• blastocyst - stem cells extracted from here
• embryonic stem cells are totipotent
• embryotic stem cells are used in therapeutic cloning
• adult stem cells are multipotent
• multipotent - can only form specific tissues or organs
• therapeutic cloning - embryo created with the same genetic material as patient, then destroyed so stem cells can be harvested
• multipotent stem cells have limited potential to develop into many different cell types
• using embryonic stem cells is unethical because they are unable to consent
• reaction - need to take immunosuppressant drugs when using embryonic stem cells
• adult stem cells could be extracted from skin, bone marrow, etc
• adult stem cells could only differentiated into some cells (multipotent)
• therapeutic cloning:

  1. remove nucleus from the patient's cell2) remove nucleus from the egg cell3) transfer the nucleus from the patient's cell into the egg cell (without nucleus)4) electric shock to make it divide5) form into embryo6) could be differentiated into specialist cells
• stem cells in plant continue to grow throughout their life
• stem cells in plant could be reverted after differentiation
• exposed part of the stem after cutting would reverted back to being in a state which forms part of the meristem