stem cells 1.2.3

• a stem cell is an undifferentiated cell with the potential to specialise into any type of cell
• differentiated cells are specialised for a particular function
• stem cells can divide by mitosis and have the capacity to differentiate into specialised cells
• differentiated cells 'switch on' and use different genes, to make different proteins and enzymes
• cells become specialised very early in life, mostly in the foetus
• specialised cells can only divide to form the same type of cell
• plant cells differentiate throughout their lives
• differentiation is permanent in animals
• cloning produces genetically identical offspring
• in plants, large numbers of clones can be produced from a tiny piece of leaf tissue, this is because a plant cell can become unspecialised and undergo mitosis many times and can then become differentiated to form a whole new plant
• a stem cell can specialise into a wide range of different cell types whereas a normal body cell can only clone itself to stay the same
• sources of stem cells are bone marrow, embryo and meristems
• stem cells can be used for growing adult stem cells
• stem cells can be used for early embryo cloning
• stem cells can be used for special insulin producing cells in the pancreas
• plants can be cloned for when they are turning extinct, for example when bananas nearly went extinct and orchids as they are endangered. this is useful to clone plants to meet demands for food and peoples needs
• stem cells can treat spinal chord injuries, diabetes, damage after heart attack, damaged bone and cartilage
• for stem cell: embryos are being used from adult cells for use in research and therapy so would never become babies
• for stem cell: it may be possible to use embryonic stem cells from the umbilical cord of newborn babies, so that no embryos need to be destroyed for the research and treatments to go ahead
• for stem cells: the embryos used are generally spare embryos from IVF treatment, which would be destroyed anyway
• against stem cells: all embryos have the potential to become babies, it is therefore wrong to experiment on them or destroy them
• against stem cells: embryos cannot give permission to be used in experiments or treatments, so it is unethical
• for stem cells: embryonic stem cells could be used to grow new tissues and organs for transplants
• against stem cells: embryonic stem cell treatments are very expensive and there is a risk that they may cause further problems such as the development of cancers
• against stem cells: it is taking a long time to develop any therapy that works - the money and research time would be better spent on other possible treatments, such as new drugs or using adult stem cells
• for stem cells: embryonic stem cells offer one of the best chances of finding treatments for many different and often very serious conditions, including paralysis from spinal injury, Alzheimers and diabetes
• a stem cell is an undifferentiated cell of an organism which is capable of dividing to produce many more cells of the same type (undifferentiated cell)
• stem cells also differentiate into different cell types
• stem cells are found in early human embryos - because the early cell types have to differentiate into all different types of cell
• stem cells are also found in adult bone marrow but can only turn into selected cells such as red blood cells etc
• stem cells can also be found in the meristem tissue of plants because plant cells differentiate all throughout the life of the plant
• stem cells from embryos and bone marrow can be grown in a lab to produce clones (genetically identical cells) and made to differentiate into specialised cells to use in medicine or research
• medicine already uses adult stem cells to cure disease, for example, stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells in the patient who receives them
• embryonic stem cells can also be used to make insulin producing cells for people with diabetes or nerve cells for people paralysed by spinal injuries
• in therapeutic cloning, an embryo could be made to have the same genetic information as the patient, so it would not be rejected by the patients body if it was used to replace faulty cells or other medical treatments
• however, the use of stem cells has potential risks such as a transfer of viral infections
• the stem cells in plants are found in the meristems of plants
• these cells differentiate throughout the plants entire life
• these stem cells can be used to produce clones of plants quickly and cheaply
• stem cells can be used to grow more plants of the same species