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DNA in mitochondria, the powerhouses of the cell, is passed down from mother to child. But there are many mitochondria in each cell, and these mitochondria may have different genetic features. If a mother carries a mixture of mitochondrial DNA (mtDNA) types, this can make it hard to say which features their children will inherit. For mothers carrying a disease-causing mtDNA mutation, this makes family planning and clinical therapies challenging.
Researchers used cutting-edge technology to reveal the mixtures of mtDNA in the egg cells of mother mice at a wide range of ages, and in the litters of offspring the mothers produced. In concert, they developed a mathematical model describing the changes to, and inheritance of, mtDNA from mother to offspring. In this study, they combined the model and data to learn how different biological processes affect mtDNA through and between generations.
They found that the variability of mtDNA dramatically increased as mothers aged, this means that the probability of inheriting lower and higher levels of a genetic feature increases for older mothers. Older mothers have a higher chance of having some eggs with low levels of a given mtDNA type. This may improve their chance of selecting eggs with low mutation levels in IVF cycles.
Researchers also discovered different mtDNA mixtures that were inherited in different ways-with some mtDNA types favoured for inheritance and some disfavoured. They used their findings to create a way to predict how the risk that offspring would inherit disease-causing mtDNA features changes over time.
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