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What different types of DNA test can you have?

2    The female line DNA test and genealogy

mtDNA testing is completely different from the Y-DNA test done to help find relationships between families through the male line. MtDNA testing gives information about the female line.

MtDNA is short for mitochondrial DNA. Like all of this DNA stuff, things can get complicated when you try to find out why. Basically, every cell in your body needs energy, it needs to convert food energy to carry out all of its jobs in the body. The energy conversion is done by a tiny cellular organ called a mitochondrion (plural mitochondria).

These small energy units look a bit like sausages – they have a folded inner membrane where all the reactions take place. A long time ago, right at the start of evolution of cells, mitochondria were originally free-living bacteria. They were enclosed inside larger cells, where they worked for the larger cell, so weren’t digested. Because they were once free living, the mitochondria in our cells today still have remnants of their DNA. This DNA is not passed down in the nucleus of a fertlised egg. It is passed from mothers to their children in the egg cell, in the cytoplasm that surrounds the nucleus.

This DNA changes very little over time and every one of us have virtually identical mitochondrial DNA (mtDNA) to our mother. The mtDNA is passed down the female line and can be used to tell if people are descended from the same woman.

What use is the mtDNA test for family history?

The picture on the left is actually a chart of the genes that are found in mtDNA. They have been carefully mapped and can be compared between different women. The rate of change over time in these genes is low - making it easy to work out if a person is descended from the same maternal ancestor as another person, and how far back their common ancestor lived.

Taken further, this technique can show how we are all related to the daughters of Eve, a group of 37 women who are the maternal ancestors of everyone alive today.

For your own family history, mtDNA testing, like other DNA tests, cannot reveal your entire family tree. Your results can be fed into databases, that are growing all the time, and you may be able to contact some closely related people. Otherwise, it can tell you if you and someone else who takes the test are closely related.

Overall, however, the mtDNA test tells you more about your ethnic origins - whether you are from a European tribe, from Africa, or from North America. Find out more about the daughters of Eve.