In medicine (genetics), a<unk> or<unk> sm denotes the presence of two populations of cells with different genotypes in one individual, who has developed from a single fertilized egg .<unk> sm may result from a mutation during development which is propagated to only a subset of the adult cells.
Although the two can have some common symptoms,<unk> sm is distinctly different from chimerism. In the latter, the two or more genotypes arise from more than one zygote, while in<unk> , these genotypes arise from only a single cell.
In rare cases, intersex conditions can be caused by<unk> sm where some cells in the body have XX and others XY chromosomes.
The most common form of<unk> sm found through prenatal diagnosis involves trisomies. Although most forms of trisomy are due to problems in meiosis and affect all cells of the organism, there are cases where the trisomy only occurs in a selection of the cells. This may be caused by a nondisjunction event in an early mitosis, resulting in a loss of a chromosome from some trisomic cells. Generally this leads to a milder phenotype than in non-mosaic patients with the same disorder.
An example of this is one of the milder forms of Klinefelter's syndrome, called 46/47 XY/XXY<unk> wherein some of the patient's cells contain XY chromosomes, and some contain XXY chromosomes. The 46/47 annotation indicates that the XY cells have the normal number of 46 total chromosomes, and the XXY cells have 47 total chromosomes.<unk> sm also sometimes occurs when a different copy of the X chromosome is expressed in different cells, such as in calico cats.
Mosaic 
Outlier
Complex 
Short Stature
Blunt 
Pedunculated
Fair coin
Grief