Archive | April 2023

Make Ancestry Find the Relationship

Did you know that Ancestry can figure out how you are related to a DNA match if you both have trees linked to your DNA tests? You do not have to have anyone further back than your parents if other relatives have more extensive trees on Ancestry that include your family,

So how do you link your tree to your DNA? First log into Ancestry.com. Then click on DNA Result Summary in the pull down menu under DNA. Next click the gear on the far right that says Settings next to it as shown in the image below.

Once you are on the Settings page, scroll down to the words DNA and family tree linking.​ Then click that box to get to the page where you can link your test to your tree.

​There you will see something like the below image​ where you can specify the tree and the person to link the DNA test to. When you start typing a name, Ancestry will use auto complete to show possible names from your tree. Once you have selected yourself or the person whose kit it is, click the blue button to make the connection.

The tool Ancestry uses to find and display relationships based on trees linked to DNA results is called ThruLines which I have numerous posts about. Now for an example of what this can produce.
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Using Segment Sizes in DNA Relationship Predictions

Segment sizes matter for predicting the closeness of a relationship. That is because inherited DNA chunks get divided up with each generation’s recombination, becoming smaller over time. It has often puzzled me that none of the DNA relationship calculators take that into account. The total centimorgans (cM) can be similar for lots of different relationships. Click here for my post on telling half siblings apart from aunt/uncle/niece/nephew relationships by using segment sizes.

Click here for Ancestry’s explanation of how they predict relationships and here for the article at 23andme. Neither mentions segment sizes.

Click this image for my slides demonstrating the DNA painter relationship calculator

My favorite calculator has long been the one at DNA Painter where the table is based on Blaine Bettinger’s collected data and the probabilities are by Leah Larkin based on the Ancestry white paper. It can work from a percentage or a cM value and lights up just the possible relationships in its table. Clicking on any table entry gets a histogram of frequencies.  I have slides showing how nicely it works, done for a recent talk about 3rd party DNA tools for the SCGS jamboree. Click the image above to see those. That video should be available to attendees from the web site genealogyjamboree.com

Recently a calculator was published at DNA-SCI which includes segment sizes by asking for the number of segments. I have used it for a number of closer relationships and have been very impressed with its results.
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