Why you should ask older relatives to take a DNA test

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15 January 2018
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Find out why asking an older relative to take a DNA test could provide many benefits to your family tree research.

Find out why asking an older relative to take a DNA test could provide many benefits to your family tree research.

Very simply, older relatives share more DNA with your ancestors than you do, giving you many more DNA matches and the chances to find out more about where your ancestors came from and to collaborate with DNA cousins.

DNA inheritance

Each individual inherits 50% of their autosomal DNA from their mother and 50% from their father. Beyond that, they inherit approximately 25% from each grandparent and approximately half the previous amount from every subsequent generation of ancestry. Eventually, due to the random nature of autosomal DNA inheritance, there will be some ancestors from whom an individual does not inherit significant portions of their autosomal DNA.

Any autosomal or X-DNA you inherit from a specific ancestor has to be less than or equal to the amount of DNA that your parent inherited from that same ancestor which in turn is a subset of the DNA that your grandparent inherited from that same ancestor. While your grandmother may share 25% of her DNA with your second great-grandparent, you will share only about 6% of your DNA with that same ancestor.

The DNA coverage concept

By testing yourself, 100% of your autosomal DNA will be represented in a database, 50% of your parents’ DNA will be represented, and 25% of each of your grandparents’ DNA will be represented in the database. Though each individual inherits 50% of their DNA from each parent, siblings inherit different 50% portions.

Though they will share some DNA in common with a sibling, they will also carry unique DNA. By testing a sibling, you could obtain approximately 75% coverage of your parents’ DNA and about 37% coverage of each of your grandparents’ DNA.

Preserving your DNA

By testing your older relatives, you ensure that their DNA will be represented in the current databases and you increase the chance that future generations will be able to connect with them through these means. It is worth noting that, currently, MyHeritage is offering users who have completed DNA testing through another service to upload their raw data for free to MyHeritage. Users will receive DNA Matches for free, useful for finding relatives based on shared DNA.

Though we as genealogists have begun to treat DNA as we would other records in our analysis, correlation and proof arguments, we also need to start thinking like archivists and dedicate time and effort to acquiring and preserving DNA records so that the information of our ancestors’ DNA will be available for future generations of researchers. Don’t wait until it’s too late. Test your older relatives today!

Extracted with permission from a blog by Paul Woodbury of Legacy Tree Genealogists. Read the blog in full.

(image copyright Charles Hamm)