Why is mitochondrial D.N.A. used in research?

Question

Why is mitochondrial D.N.A. used in research?

Answer 1

Depends on the research....  Mitochondrial DNA (mtDNA) is inherited maternally.  That is, it is passed on from mom to all kids because the  mitochondria in a zygote (fertilized egg) come from the egg, not the sperm.  

It does not recombine.  That is it does not mix mom and dad's DNA by crossing over. Therefore, you can trace ancestry more easily.

The entire sequence (which is small compared to the DNA in the nucleus) is not only known, but well known for all the variations.  Although the human genome (nuclear DNA) has been sequenced, knowledge of all the variations is slight.

Most importantly, for CSI and the like, each cell can have thousands of mitochondria, and thus thousands of copies of mtDNA, but only one nucleus.  So, if you have a small sample to extract DNA from (i.e. a little blood drop), you'll have much more mtDNA, than nuclear DNA.