Mosaicism describes the presence of two populations of cells with distinct genotypes within a single organism

  • It is caused when either mutation or division error creates two distinct cell types which divide into separate cell lines

Mosaicism is more pronounced when errors occur in early embryo development and thus affects a greater proportion of cells

  • X-inactivation in mammals creates a mosaic of genotypes linked to the X chromosome only, and hence is not true mosaicism