In genetics, a chimera is an individual with 2 or more distinct, unrelated genetic lineages (ie, 46XX/46XX, 46XX/46XY, or 46XY/46XY). This condition is not to be confused with germline mosaicism, in which a mutation occurs during mitosis, altering part of a genetic line (aneuploidy). In mosaics, typically transcription errors result in a chromosome that may be either duplicated or deleted. The mutated cell is further copied, appearing separate from other cells (46XX/47XX or 46XY/47XY) but in fact, a single lineage exists. An individual with germline mosaicism shouldn’t have any related health issues since it is not a systemic mutation. An example of mosaicism where a systemic mutation exists is Trisomy 21, or Down’s syndrome, where a duplicating error occurs on chromosome 21 affecting all or nearly every cell.