A condition wherein two or more cell populations with different genotypes exist in an organism, derived from a single zygote, as a result of experimental manipulation or to faulty distribution of genetic material during mitosis.
For example is the rare condition wherein some cells of the body of a patient have XX chromosomes while other cells have XY chromosomes. Another example is the 46/47 XY/XXY mosaic in which the individual contains two sets of cell populations: (1) a population of cells with the normal 46 number of chromosomes and XY genetic constitution, and (2) a cell population with 47 chromosomes and XXY genetic consititution.
Word origin: mosaic + -ism
See also: sex chromosome