In each generation, it is possible for the child to inherit the heteroplasmic genome, only the ancestral genome, or only the descendant genome. For each generation, if the mother has a heteroplasmy, each of her children will experience any one of these outcomes:

  • The child has a heteroplasmy at the same position. The child inherited some mitochondria with the ancestral genome and some with the descendant genome. Thus, the child has some of each in his or her cells. The proportion of ancestral to descendant genome can vary in each generation and in each child.
  • The child has only the descendant genome. Only mitochondria with the mutation were passed on to the child. If the child is female, then her children will also inherit only the descendant genome. The new mutation is then fixed in her descendants.
  • The child has only the ancestral genome. Only mitochondria without the mutation were passed on to the child. If the child is female, then her children will also inherit only the ancestral genome. The new mutation is then lost in her descendants.

Therefore, heteroplasmy may last for many generations. Between 15 and 70 generations is normal for humans. However, about 120 generations (3,000 years) are required for there to be a 99% chance that the new mutation has become fixed in the descendants who have it.

Sources:

  • Ballard and Whitlock, M. C. (2004). The incomplete natural history of mitochondria. Molecular Ecology, 13(4):729-744.
  • Kumar, S., Tamura, K., and Nei, M. (2004). MEGA3: Integrated software for molecular evolutionary genetics analysis and sequence alignment. Briefings in Bioinformatics, 5(2):150-163.
  • Millar, C. D., Dodd, A., Anderson, J., Gibb, G. C., Ritchie, P. A., Baroni, C., Woodhams, M. D., Hendy, M. D., and Lambert, D. M. (2008). Mutation and evolutionary rates in adélie penguins from the antarctic. PLoS Genet, 4(10):e1000209+.