B3 - Stem Cells, Differentiation & Growth

Animals stop growing, plants can grow continuouslyPlants and animals grow differently: Animals tend to grow until they reach a finite size (full growth) and then they stop growing. Plants however, often grow continuously, even really old trees still put out new branches In animals, growth happens by cell division but in plants, growth in height is usually due to cell enlargement. Growth by cell division usually just happens in areas of the plant called meristems which is at the tips of the roots and shoots

Stem cells can turn into different types of cells Differentiation is the process by which a cell changes to become specialised for its job. In most animal cells, the ability to differentiate is lost at an early age but in plants this ability is not usually lost Most cells in the body are specialised cells for particular jobs Some cells are undifferentiated, they can develop into different types of cells, organs and tissues depending on what instructions they are given Stem cells are found in early human embryos, they can turn into any kind of cell at all  Adults also have stem cells but these are found in certain places in the body such as in bone marrow 

Stem cells may be able to cure many disorders Medicine already uses stem cells to cure disease, e.g. people with blood disorder e.g. (leukemia and anaemia) can be cured using bone marrow transplants. Bone marrow contains adult stem cells that turn into new blood cells Very early human embryos contain lots of stem cells. Scientists can extract them and grow them. They think they may be able to grow tissues to treat medical conditions. This is known as stem cell therapy

Some people are against stem cell research Some people believe that stem cell research is bad because an embryo is a potential human life, others think that curing patients who already exist and are suffering is more important than the rights of embryos Embryos used in the research are usually unwanted ones from fertility clinics that if they weren't used in testing would probably be destroyed Around the world there are 'stocks' of stem cells that are used for research. Some countries like the USA, are not funded stem cell research

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