Preimplantation genetic screening (PGS) can be used to quantitate the risk of a child of being affected by a mitochondrial disease. In most cases, a muscle mutation level of approximately 18% or less confers a 95% risk reduction. Sequence illustrating<unk>  genotype of 16169 C/T in Nicholas II of Russia.
Heteroplasmy
Allelic heterogeneity
Genetic heterogeneity
Variegation 
Phenotypic heterogeneity
Dynamic mutation
Non-Mendelian inheritance
Low copy repeats