DNA Testing – what will you find?.

DNA Testing – what will you find?

A person’s ancestry is written in their DNA. The evidence can be used to trace deep ancestral origins, especially when researchers run out of historical documents to work from.

In the rush to be DNA-tested, we rarely stop to consider what we will find, and what information it will tell us.

DNA research is based on comparison-studies. When a company tests your DNA sample, it compares it to other DNA samples stored in its knowledge bank. So, the comparison is only as good as the number and types of tests done, and the diversity of groups tested.

Six years ago, a good friend, a lady who could document her family history back 15 generations in Ireland, England and Scotland, showed me the results of her DNA test-results completed by an American company. Much to her disgust, she was recorded as ‘European, indeterminate.’

“My Scottish granny…” she fumed, “…is spinning in her grave.”

At that time, the number of Irish and British tests completed by this U.S. based company were so small, that DNA-testing was about as relevant to her, as a horoscope.

The moral of the tale is, when you test your DNA,

There are three types of DNA tests:



Mitochondrial DNA, can tell you about your direct line maternal ancestry (mother’s mother’s mother, etc.) and has value in looking at deep roots (pre-historic)


This is test that men can take of their Y chromosome, and will tell you about your direct line paternal ancestry (father’s father’s father, etc.). It’s very useful in pinning down surname origins.

Autosomal DNA

This tests a selection of your entire genome. It’s especially good for tracing relatives back 5 or 6 generations (maximum). After 5/6 generations it breaks down as a useful tool for identifying relationships. However, it can also be used to determine geographic roots, in a variety of ways.

Currently these are the best / most reputable companies listed in alphabetical order.

  1. Ancestry does the Autosomal DNA test only. They have spear-headed geographic clustering/matching and recently released their Genetic Communities test which has 16 distinct regions for Ireland (and many more for the rest of the world) which is the highest resolution available at the moment. For cousin matching they still have a small Irish sample base.

Irish readers probably saw the results on the Late Late Show a few weeks ago.  The “100% Irish” result, based on a “gold-standard” doesn’t carry any great weight. However their Genetic Communities are much more useful for your research and well worth doing.

  1. Family Tree DNA is the company that’s been around for the longest. They do all three tests at various resolutions. It’s the best place for YDNA tests and group/volunteer projects

  1. Living DNA do all three DNA tests, and are excellent for Britain. They are only starting to develop Ireland. They offer the best geographic distribution resolution of any of the tests I’ve seen for Britain, but not yet Ireland.

  1. The Royal College of Surgeons, Ireland is also running a genetic genealogy project in partnership with the Genealogical Society of Ireland. This holds out the hope of even better resolution to geographic matching if and when they make their results and data public.

The RCSI’s own press release is online here https://www.rcsi.ie/index.jsp?n=110&a=1966

The project is headed by Professor Gianpiero Cavalleri, a medical scientist. The genealogical aspects of the project will be directed by the Genealogical Society of Ireland.

Participants are sought from all parts of the island of Ireland who can trace their eight great grandparents to a general area – for example, south Co. Wicklow / north Co. Wexford – areas within say 30kms radius of the main homestead.

Participants are free to choose whether to partake in both the ‘historical’ and ‘health’ studies or indeed, just the ‘historical’ if they so wish.

If you are interested in taking part in the project email Irish.DNA@familyhistory.ie


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