Mitochondrial DNA (mtDNA)
Definition
DNA located in mitochondria rather than the cell nucleus. Present in hundreds to thousands of copies per cell, making it recoverable from highly degraded samples including processed bone, dried tissue, and heat-treated products. Maternally inherited, so it identifies species and maternal lineage but cannot distinguish between individuals from the same maternal line.
- Location
- Mitochondria, outside the cell nucleus
- Copy number
- Hundreds to thousands of copies per cell
- Inheritance
- Maternal line only
- Best use case
- Highly degraded samples: bone, dried tissue, heat-treated material
- Key limitation
- Cannot distinguish individuals sharing a maternal line
Common questions
Why is mtDNA preferred for badly degraded samples?+
Because each cell holds hundreds to thousands of mitochondrial copies compared to just two copies of nuclear DNA, mtDNA is far more likely to survive in enough quantity to sequence after heat, decomposition, or long environmental exposure has destroyed most nuclear DNA.
Why can't mtDNA identify a specific individual?+
Everyone related through the maternal line, such as siblings or a mother and her children, shares essentially the same mtDNA sequence. It narrows identification to a maternal lineage or confirms species, but nuclear STR profiling is still needed to distinguish one person from a sibling.
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