Stem cells and differentiation · Grade 11
A fertilised egg divides again and again. At first all the new cells are the same, but soon they differentiate: they become specialised for one job, as nerve, muscle or blood cells. A stem cell is a cell that has not yet differentiated. It can divide to make more stem cells and can become other types of cell, which is why stem cells may one day treat many diseases.
Key facts
- Differentiation is the process by which a cell becomes specialised for a particular job. It gains the sub-cellular structures it needs, such as many mitochondria in a muscle cell.
- Most animal cells differentiate at an early stage. In mature animals, cell division is mainly for repair and replacement. Many plant cells can differentiate all through the plant's life.
- Embryonic stem cells, from early human embryos, can become almost any type of human cell. Adult stem cells, such as those in bone marrow, can form only some types, such as blood cells.
- Meristems at the tips of roots and shoots can make any type of plant cell throughout the plant's life. They are used to clone plants quickly and cheaply: rare species, and crops with useful features such as disease resistance.
- Stem cells could treat conditions such as diabetes and paralysis. Bone marrow transplants already use adult stem cells to treat leukaemia.
- In therapeutic cloning, an embryo is made with the same genes as the patient. Stem cells from it are not rejected by the patient's immune system.
- There are risks and objections: cells grown in a lab could pass on a virus; some people object to destroying embryos, which they believe have a right to life.