Tag Archive | Ashkenazi DNA

How Related Are Ashkenazim?

Feb28

Eight of the ten fully Jewish kits I have access to showed related parents in the “Are Your Parents Related”  (AYPR) tool on GEDmatch. I am wondering if this level of relatedness (about a 4th cousin) is generally true among Ashkenazim and other endogamous populations. Or perhaps the GEDmatch parameters need some tweaking?

Sample related segment from a Jewish kit in AYPR

Sample related segment from a Jewish kit in AYPR

Also a number of married jewish couples I know have discovered that they share a DNA segment. Personally I share 11 cM on the X with my late husband even though I have only one Jewish grandparent. Most testing companies show me as about 30% Jewish.

I can understand that when people live in the same general area for generations, one could easily marry 3rd and 4th cousins. I also know that in the past, cousin marriages were not uncommon among Jews.

I invite all tested fully Jewish people to run that free tool at GEDmatch and then fill out my form on the next page. Please fill it out even when they are not showing as related to help with my statistics.

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A Sperm Donor is Found with DNA

Jul15

The DNA results are in and they confirm that we have found the sperm donor, my late husband’s second cousin once removed. This cousin now has 8 children instead of none. Back then, donors were promised anonymity, but DNA testing has changed that; if their close family or cousins have done DNA testing, then it is likely that they can be identified. Continue reading →

More on Ashkenazi DNA

Mar23

It is time to update my recommendations on dealing with Ashkenazi Jewish DNA, the DNA of those who are Jewish of Northern European origin, often abbreviated AJ. The usual goals of DNA testing are to find out where your ancestors were from, to find cousins who might have good family stories, to confirm your paper genealogy, and perhaps to check on health issues. There are some special considerations for AJ DNA.

First, for Ashkenzi Jews, the ethnicity results are usually not very useful as they look like this:

Image of Typical Ashkenazi Jewish DNA Origins

Typical Ashkenazi Jewish DNA Origins as shown at Ancestry.com

Of course for some with a larger than 2% non-Jewish percentage, it can confirm a non-Jewish ancestor.

Another deep ancestry goal for the Jewish male is to confirm or look for Cohanim or Levite roots. If your Y haplogroup belongs to one of those (see below) then best to do full Y testing over at Family Tree DNA which has projects for Levites and various Cohen groups. 23andme gives you your high level haplogroup but the other testing companies do not. If you tested elsewhere, click here and scroll end of this article to learn how to get your Y haplogroup: Why Y?.

Diaagram of Jewish Y Haplogroups

Slide on Jewish Y Haplogroups – image from a Y haplogroup crative commons image at wikipedia, no longer available

Finding relatives is difficult because all of us Ashkenazim are related multiple times, both way back when and more recently. Most AJs look like 4th or 5th cousins to each other even when that is not the case.  Cousin marriages, uncle-niece marriages, and other close family marriages abound in our trees. In my own family, on my Jewish line, my great grandmother fixed up her sister with her husband’s brother to get that dowry for the family business so I have double third cousins. Click here for my article from back in 2014 that suggested that we are all descended from 350 people in the 1300s.

This means the Shared Matches feature at Ancestry is useless to us because it does not show how the two matches are related to each other and that can be quite distant. Both MyHeritage and 23andme are kind enough to show how the shared matches are related to each other.

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Ancestry and the Longest Segment

Aug30

All the DNA testing companies, except Ancestry, show you a chromosome map of the segments you share with a DNA match. For the casual user those maps, called chromosome browsers, may not be of interest. However those of us with intermarried families among our ancestors (endogamy) need to see the segments in common in order to know if a match is a findable relative who shares large chunks of DNA with us or just someone who shares multiple distant ancestors. Third cousins and closer family will always share some large segments, at least 20 or 30 centimorgans and even larger for closer relatives (see Blaine’s chart below).

Ancestry now shows the longest segment on a DNA match’s profile page which could be very useful to help decide which matches to pursue and which ones to ignore.

A known fourth cousin on my Norwegian line with some endogamy, notice how much larger his largest segment is than the size of the match

A word of warning, the size of the largest segment that they show is uncut, that is it is listed before they remove matching DNA that is expected to be population specific. For example, many of my one segment matches show a longest segment that is larger than the match size as shown above! If you click on the longest segment number there is a very informative popup about relationships and segments that includes this statement:

“In some cases, the length of the longest shared segment is greater than the total length of shared DNA. This is because we adjust the length of shared DNA to reflect DNA that is most likely shared from a recent ancestor. Sometimes, DNA can be shared for reasons other than recent ancestry, such as when two people share the same ethnicity or are from the same regions.”

A Jewish match not to pursue, likely related many times since the largest segment is 15

My often requested advice for Ashkenazi Jewish researchers is to look for one segment greater than 20cM and another greater than 10cM plus several others in order for a DNA match to be recently related enough to find the common ancestor(s). Therefore it would be even better if Ancestry showed the two largest segments. Subtracting the largest segment from the total to figure out the sizes of the other segments is not very accurate since the total is adjusted by removing population specific sections (Timber algorithm) while the largest is not.

Blaine Bettinger includes the longest segment in his DNA statistics collection form and below is a chart of those 2015 results by cousin level; click here for his blog post.

Chart of longest segment statistics collected by Blaine Bettinger. Click it for the full article

I spent some time looking at the cases where matches are tested at both Ancestry and 23andme in my family’s results.

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Using Ashkenazi Jewish DNA to Find Family

Nov10

Reading about this holocaust survivor’s discovery of missing family via DNA had me crying –
http://www.ynetnews.com/articles/0,7340,L-4589762,00.html – but it also got me thinking about how few jewish DNA success stories there are. Perhaps that is changing now that more people are testing.
A7734 on facebook
The screenshot at the left is from facebook page A7734 about Menachem’s search. It shows him and the genealogist who helped him, looking at the first picture of his parents he had ever seen.

Frankly, success stories with jewish DNA are rare.  I have none to report from my family. I emailed all my Ashkenazi researching friends to see if anyone had a good success story. Not very many are out there. If you have one, please send it along.

The endogamous nature of jewish DNA is part of the problem. Everyone looks like a close relative in the DNA matching. Another part of the problem is that so few Ashkenazim know their ancestors past their great-grandparents. Too many records were destroyed in WWII, among other problems researching.

In my experience, if an Ashkenazi Jewish (AJ) DNA match is not showing as a 2nd cousin or better it is unlikely that you will find the relationship. An experienced Israeli researcher told me to ignore anyone without at least one long segment match of 23 cM.

Below are a few tips from search angel Gaye Tannenbaum who frequently works with AJ DNA.

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