Mitochondrial DNA and human evolution. (Answer in 150 words)

- Mitochondrial DNA and human evolution. (Answer in 150 words)
Introduction
Mitochondrial DNA was the first molecule of human prehistory, because it behaves as a single unbroken maternal record.

Body
1. Its properties: a small genome of 16,569 base pairs in hundreds of copies per cell, so it survives in degraded and ancient bone. Paternal mitochondria are destroyed at fertilisation, so inheritance is maternal and recombination absent; mutation runs about ten times faster than nuclear DNA, concentrated in two hypervariable segments.
2. How it is used: shared mutations define haplogroups, which are built into coalescent trees dated with a calibrated clock. Cann, Stoneking and Wilson rooted the tree in Africa in 1987, giving Mitochondrial Eve near 200,000 years. Haplogroups M and N mark the out-of-Africa founders; India's deep M diversity supports a single southern-route dispersal.
3. Findings and limits: it established recent African origin, and the 1997 Neanderthal sequence fell outside the modern range. But one locus is one lineage, not a population; the clock rate is disputed; and archaic admixture shows only in the nuclear genome.

Conclusion
It remains a robust tracer, now read alongside Y-chromosome and whole-genome data.