The cell in the top left is heteroplasmic as shown by the normal mitochondria in purple and the mitochondria with a mtDNA mutation in red. As this cell divides, the mitochondria replicate and independently assort into the daughter cells. This leads to both positive and negative (cell shown in red) homoplasmy.
Homoplasmy is a term used in genetics to describe a eukaryotic cell whose copies of mitochondrial DNA are all identical.[1] In normal and healthy tissues, all cells are homoplasmic.[2] Homoplasmic mitochondrial DNA copies may be normal or mutated;[1] however, most mutations are heteroplasmic[2][3] (only occurring in some copies of mitochondrial DNA). It has been discovered, though, that homoplasmic mitochondrial DNA mutations may be found in human tumors.[4]
The term may also refer to uniformity of plant plastid DNA, whether occurring naturally or otherwise.[citation needed]
^Coller, HA; Khrapko, K; Bodyak, ND; Nekhaeva, E; Herrero-Jimenez, P; Thilly, WG (2001). "High frequency of homoplasmic mitochondrial DNA mutations in human tumors can be explained without selection". Nature Genetics. 28 (2): 147–50. doi:10.1038/88859. PMID11381261. S2CID11929018.