Sunday, April 9, 2017

What can you do with small ethnic percentages?

Author and DNA expert Blaine Bettinger posted this great Genetic Genealogy Tip:on his Facebook group.

Small ethnicity percentages (1 to 2% or less). What can we do with those? Which are real and which are noise? Here's what I do, and I'd love to hear what others do. I do not take small percentages at face value; instead, I analyze them with multiple calculators, preferably where I can "see" the segment(s) on the chromosome(s).

For example, let's say I've tested at 23andMe, and there's a single Native American segment on chromosome 3. I take the raw data to GEDmatch and use SEVERAL calculators (my favorite is Dodecad World9) to determine whether the same segment is identified on chromosome 3. Identifying the same segment using two or more calculators, which typically use slightly different algorithms and reference populations, vastly improves my confidence in the characterization of that segment as being Native American.

If you've tested at AncestryDNA or Family Tree DNA, you won't have the initial chromosome painting, but you can still use GEDmatch to perform the segment identification using multiple calculators.

I never use just percentages anywhere. I always visualize the segments on the chromosomes.

[One other trick - look for the segment in multiple generations. For example, is the segment there in a previous or later generation? Is the segment larger in a previous generation? If you see it in the same place in multiple generations, that again increases my confidence.]