Question

What makes mitochondrial DNA useful as a molecular clock?

Answer 1

A slow mutation rate makes it useful for determining evolutionary relationships between ancient species.
Mitochondrial DNA stay almost identical over species and only varies ever so slightly. By comparing mitochondrial DNA over species you are able to see how closely related they are and how long it might have taken for the species to evolve.
I hope this helps! :)

Answer 2

1.mitochondrial DNA avilble at high level as compare to nuclear DNA,
2.Maternal inhertance
3. Small so easily sequenced