See also: Mosaic

The mosaic is a form of genetic disease. It is the fact that an individual has at the same time healthy cell S and cells presenting a genetic anomaly. The origin is in the first stages of the development, when that there are only some cells which will constitute the Embryon. Certain cells are healthy and give rise to healthy a line of cells, others present an anomaly and give a line of cells abnormal. There are several possible causes of such a difference:

• a change during the division of a cell

• chance at the time of the inactivation of the X chromosome