If you have take a Y-DNA test as part of our project, I hope this post will help you understand the results you can see when you log into your FTDNA account or look at the project reports.
What Gets Tested?
A chromosome contains sequences of repeating nucleotides known as short tandem repeats (STRs). The number of repetitions varies from one person to another. Y-DNA testing involves looking at STR segments on the Y chromosome, which are referred to as markers. The test reports the number of repeats for each STR, which is shown as the marker’s value. The Y-DNA37 test looks at 37 specific markers.
You can see your test results by selecting Y-STR results in the Paternal Ancestry section. Each STR has a DYS number (DNA Y-chromosome Segment number). In the example below, the value of the DYS393 marker is 13. This means the DYS393 sequence of nucleotides is repeated 13 times – or we can say the value of that marker is 13.
It’s these values that are compared to those of others in the DNA project. You can see the results by looking at the Classic or Colorized project results.. The image below is the Colorized chart, which highlights where the mis-matches are.
Interpreting Your Y-DNA Matches
Your YDNA matches will look like those below (names are removed for privacy). The first column shows the genetic distance between you and the match. This does not tell you how many generations away you match; it shows the number of differences in the values for the STR markers. The second column has small icons under each name. The first lets you email the match. The orange TIP button shows you the likelihood of you having a common ancestor with the person – see later. The next icons allow you to add a private note to the match, and to view their family tree, if they have uploaded it to FTDNA. Finally, it shows which tests the person has taken – Y-DNA37, Y-DNA67, Y-DNA111, Big Y, or the autosomal test (FF).
The next column gives their earliest known ancestor, if they have given this information. The Y-DNA Haplogroup column shows either the predicted or confirmed haplogroup of the individual (unless the person has tested at Big Y level, this will be a prediction only.) In the image above, only one of the matches has tested at Big-Y level. Until a confirmed haplogroup is known, there will be nothing in the Terminal SNP column. The final column on the right shows the date of the match.
How Far Back Do You Match? The Y-DNA TIP Report
To find out how many generations ago you may have had a common ancestor with any of your matches, click on the TIP button under their names. This will bring up a Y-DNA TIP report like the one below:
You can see the percentage probability that you share a common ancestors within a certain number of generations. In the chart above, it is known that there was no common ancestor for at least 5 years, which has been set in the lower part of the report. FTDNA uses a complex algorithm to calculate the number of generations. It takes into account the number of markers that do not match, but also considers how quickly those markers mutate, as some change more frequently than others.
Haplogroups and Big-Y Test
We now have some project members who have taken the Big-Y test, which looks at 700 markers, rather than the 37 in the Y-DNA37 test. My next post will explain what has been discovered by those tests.
