(a) Cellular differentiation is the process by which a cell develops more specialised functions by expressing the genes characteristic for that type of cell.
Differentiation into specialised cells from meristems in plants; embryonic and tissue (adult) stem cells in animals. Stem cells are relatively unspecialised cells in animals that can continue to divide and can differentiate into specialised cells.
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Multicelluar organisms consist of a variety of cell types, each of which are specialised for a particular function. This phenomenon, known as a division of labour means that the cells can perform a single function more efficiently.
Differentiation is the process in which unspecialised cells become specialised for a particular function. They can alter their shape or biochemistry.
All somatic (body) cells are derived from the zygote through division and so contain all of the genetic information to produce every cell in the body. Every single gene could be expressed, if the cell required it. If a gene is expressed the cell produces the protein which it encodes.
Differentiation
There are some genes, producing proteins essential for survival which are switched on in all cells (e.g genes encoding the respiratory enzymes) regardless of their function. However, during differentiation of a cell to become a specialised cell, a group of genes, encoding proteins which relate to the specialised function of the cell become expressed (switched on) and a second group of genes, which produce proteins not required for the cell’s function are not expressed (remain or become switched off).
In the example below, the haemoglobin gene is switched on in the red blood cell, but switched off in all other cell types which do not require haemoglobin to function.
