Stem Cells

• When an egg is fertilized, a single non-specialised cell is formed which then divides to form a ball of non-specialised cells. This is the basis for every multicellular organism
• Unspecialised cells do not have the specific shape or features found in cells specialised to a function.
• Stem cells are cells which can express all of their genes and are able to divide by mitosis.
• Stem cells can divide by mitosis to produce more stem cells.
• Stem cells contain all of our DNA and can 'turn on' any genes in our genome: allowing them to become any type of differentiated cell.
• As an organism continues to develop and become more complex, cells start to resemble more specialised cells.
• As cells become specialised, they start to change shape and change the number and type of organelles for their function.
• once a cell is fully specialised, it is unable to divide by mitosis.
• The process of cell differentiation is when stem cells become more specialised into different types of specialised cell.
• Totipotent cells can differentiate into any cell type and form viable tissue.
• Pluripotent cells can give rise can give rise to any type of cell but cant form viable tissue on its own. Pluripotent cells are found in embryos.
• Oligopotent cells can only differentiate into a few types of cells within a single cellular such as the myeloblast stem cells which produce the 3 types of white blood cells.
• unipotent cells can only produce one cell type but have the property of self renewal. an example of these are epidermal cells (producing skin).
• Multipotent stem cells can only differentiate to give rise to cells of closely related cellular families. Such as eye and brain cells.