Which ethnic group would this person be most genetically similar to?

[Billyh]

This person is 50% Northern European, and 50% Ashkenazi Jew. Which ethnic group would they have the closest genes to?

[passenger]

In terms of autosomal composition and where they would plot on a PCA in relation to others, they would most likely be closest to Northern Italians or similar populations.

[Billyh]

That's what I would have originally thought, and that's what PCA's an autosomal DNA charts would seem to suggest, but what I have wondered about is what impact the increased shared DNA between Ashkenazic Jews would have.

[passenger]

That's what I would have originally thought, and that's what PCA's an autosomal DNA charts would seem to suggest, but what I have wondered about is what impact the increased shared DNA between Ashkenazic Jews would have.

I don't see why that would have any impact in terms of overall autosomal similarity. For autosomal DNA you inherit 50% from each parent. Higher consanguinity/bottleneck effect on the Ashkenazi side wouldn't give it any more or less weight. It will probably result in this person having a lot more DNA matches on the Ashkenazi side but that's not related to overall genetic similarity.

[Billyh]

Ah, I see. Thank you very much for answering, I am new here, and not entirely familiar with how genetics work. If you could just explain to me, why wouldn't having more DNA matches = more genetic similarity? Sorry if this is a dumb question.

[passenger]

Ah, I see. Thank you very much for answering, I am new here, and not entirely familiar with how genetics work. If you could just explain to me, why wouldn't having more DNA matches = more genetic similarity? Sorry if this is a dumb question.

No worries. We all have to be new to this at one point, and I still have a lot to learn myself.

You can take my example, for instance. My ancestry is half Jewish and half Northwestern European. Predictably I tend to plot among Northern Italians. On MyHeritage and FTDNA I have far more matches from my Jewish side than my NW European side. This could be partly because of the people the sites have in their database, but it's also because the "Ashkenazi effect" tends to grossly inflate the number of cousin matches a person has, even though some companies try to compensate for it. Using rough terms, and as you may know, judging from your previous post, what happens with Ashkenazi Jews is that because they all trace a large part of their ancestry to the same small group of Medieval ancestors, whose descendants remained relatively endogamous over the centuries, they tend to share many small segments of DNA which get "recycled" from generation to generation. This means that two Ashkenazi Jews who do not share any direct ancestors within the past two centuries might appear to be much closer cousins than they really are, since those small segments of shared DNA build up to give the appearance of a closer relationship, and it also tends to multiply the number of cousin matches you have beyond any point which is meaningful in terms of trying to trace your own genealogy.

However, this does not make me genetically any closer to my Jewish side than my NW European side. If anything, ethnicity estimates tend to make me appear more NW European than Jewish. This can happen because Ashkenazi genes, though primarily a combination of Southern European and Middle Eastern ancestry, also include Central/Eastern European components which get "wrongly" assigned to a Western or Central European category instead of Ashkenazi Jewish. It can also sometimes happen because the algorithm, instead of making a clear divide between one side of my ancestry and the other, assigns part of it to a group that is halfway in between where my maternal and paternal ancestries really are. This tends to happen more with calculators from GEDmatch or Global25 than with commercial services, but it seems to also sometimes affect commercial test results. In essence, however, my DNA is still 50% from each side, and I consistently plot in Northern Italy in the middle of where my parents plot, so the rest of this doesn't really affect what the overall average looks like.

Hope that helps.

[mokordo]

This person is 50% Northern European, and 50% Ashkenazi Jew. Which ethnic group would they have the closest genes to?

Which Ashkenazi group and which Northern European country exactly?

[mokordo]

Sorry, the text that was here should have been posted in a different thread.

[Billyh]

However, this does not make me genetically any closer to my Jewish side than my NW European side. If anything, ethnicity estimates tend to make me appear more NW European than Jewish.

It's funny you mention this, because if you look at my other post it is an example of that happening. I tried not to reveal too much info about the ethnicity in question or whose sample it was, because It's actually not my sample (I said it's mine, but it's really one of my relatives) so I don't want to do anything the person the sample belongs to would feel uncomfortable with, but it is a 50% ashkenazi component that is removed and it shows that the persons ancestry could only have been 43% ashkenazi and 57% N. European

I was under the assumption that because ashJ share more DNA amongst eachother then the outsider would have more of a dna connection to them, but I guess that doesn't make sense if you look at it as overall genes shared instead of 'number of long enough segments to be declared cousins' shared