Mosaic (genetics)

In genetics, a mosaic or mosaicism denotes the presence of two or more populations of cells with different genotypes in one individual who has developed from a single fertilized egg.

Mosaicism can result from various mechanisms including chromosome non-disjunction, anaphase lag and endoreplication. Anaphase lagging appears to be the main process by which mosaicism arises in the preimplantation embryo. Mosaicism may also result from a mutation during development which is propagated to only a subset of the adult cells.