Yes-- the inheritance of mtDNA is maternal, but interestingly not 100% of her children will inherit the disease. This is because the mother will have a mix of m

Yes-- the inheritance of mtDNA is maternal, but interestingly not 100% of her children will inherit the disease. This is because the mother will have a mix of mutated (diseased) mtDNA and wild-type (healthy) mtDNA in each of her cells, including her eggs. Some of the eggs will have close to all mtDNA mutated, but many will have a relatively low mutational burden. (This variation amongst the mother's cells and eggs is called heteroplasmy). Most mitochondrial genetic diseases have a heteroplasmy threshold (varying by gene/pathway, between 30-90% for many); when the overall burden in a fertilized egg is above this threshold, the disease is manifested in the offspring. Thus, another way to circumvent the transmission of mtDNA diseases is by using regular in vitro fertilization, and checking one of the cells at the 16 or 32 cell stage for their heteroplasmic content. Here are some references: Lightowlers, R. N., Taylor, R. W., & Turnbull, D. M. (2015). Mutations causing mitochondrial disease: What is new and what challenges remain? Science, 349(6255), 1494–1499. http://doi.org/10.1126/science.aac7516 http://doi.org/10.1126/science.aac7516 Taylor, R. W., & Turnbull, D. M. (2005). Mitochondrial DNA mutations in human disease. Nature Reviews Genetics, 6(5), 389–402. http://doi.org/10.1038/nrg1606 http://doi.org/10.1038/nrg1606 Smeets, H. J. M., Sallevelt, S. C. E. H., Dreesen, J. C. F. M., Die Smulders, C. E. M., & Coo, I. F. M. (2015). Preventing the transmission of mitochondrial DNA disorders using prenatal or preimplantation genetic diagnosis. Annals of the New York Academy of Sciences, 1350(1), 29–36. http://doi.org/10.1111/nyas.12866 http://doi.org/10.1111/nyas.12866