Could my DNA be seriously skewed?

Question

My mom and dad are 1st cousins 1x removed.  Paternal gr-grandmother and maternal grandfather are siblings.  I've just started a week ago on WikiTree so I don't have a lot of my ancestors in here yet but my tree is about 15 years in the making and the connections to both my parents through the generations is incredible, like some sort of giant wreath rather than a tree!  My ancestors on my maternal side and paternal side were related long before my parents were born.  

With the close family connection, I'd imagine that my DNA is seriously skewed!  My paternal gr-grandmother is also my gr-aunt, her mother is my gr-gr-grandmother as well as my gr-grandmother on my maternal side.  MtDNA is straight up the maternal line, XDNA comes from pretty much everywhere except the paternal line.  I understand this.  AUDNA is from all ancestors which is the test I have taken through Ancestry.  

Both my parents and all of my grandparents have passed.  I had a paternal aunt and a maternal uncle's DNA taken as well. These two are 1st cousins 1x removed.  Interestingly, my paternal African DNA is showing up in my DNA, but not that of my paternal aunt's DNA.  I wonder why?

Answer 1

Hi Donna,

I learned recently that the number of ancestors who contributed to our X-DNA is actually less than all of mom's tree.  Here is a very useful article that has these charts and a detailed explanation that I found enlightening:

http://www.genie1.com.au/blog/63-x-dna

Comments

That's terrific, thank you Keith!  I'll have a good read later about it to better understand it all!

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And it's a Fibonacci sequence.  1, 1, 2, 3, 5, 8, 13, ...  That guy turns up everywhere.

Answer 2

At the top of your tree you have a whole set of brick walls and you don't know what lies beyond.  So you don't know what DNA was in each line to start with.  Where it passed through on the way down is irrelevant.

So you can't make assumptions about which direction your ethnicities come from.  You have to test cousins to find out what comes from where.

Even then, if you're 5% Scot and your cousin is 5% Scot, it doesn't mean you both got it from the same Scot.  Really you'd need to pin down the actual shared segments.

Perhaps one day.  But what you get at present is just for fun and you can't analyze it.

Comments

Yes, it is fun but confusing at the same time!  I know that it's the roll of the die as to what segments you get and your DNA can be very different from a sibling's DNA but when your own paternal grandmother is also your 2nd cousin and your paternal gr-grandmother is also your aunt, that's gotta make for some pretty crazy mixed up DNA and I wonder if my results are skewed!

Answer 3

Sounds like you may be looking at endogamy where close relations marry each other for one reason or another. This is very common in some Jewish communities.

http://www.endogamy-one-family.com/

Try to borrow this book - it's enlightening.

Comments

The close connection with my mom and dad was not intentional I don't think.  They may not even have known they were so closely related since the families didn't seem to interact with each other back then.  I don't know that the Catholic church would have allowed it at the time.  The connection generations ago is actually pretty common where I'm from. I could probably take two random people from around here and connect them somewhere within the last 6-7 generations.  Most of my family are from south eastern Ontario and Quebec, Canada. The common ancestor that ties my paternal and maternal lines together for the last few generations is French European.

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Oh yes, the French Canadian connections are, to some degree, endogamous. And it's more than likely they didn't know of the connection.

After all, my great aunt married her half brother and we're very certain they never knew. In fact his mother was probably not sure for she was married at the time and he could have been her husband's child. We found this out with an unexplained DNA match.

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I have a feeling a lot of this went on in my family way back!  It seems that some of the mothers often died in childbirth and the fathers remarried and there would be a lot of half siblings.  Throughout my tree (or wreath!), there are a lot of common names that can be traced back to a common ancestor.  I'm going in circles a lot with this research!  Again, like my original post, I wonder how skewed my DNA is because of this.

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This FB Group is excellent for working with DNA matches. There are also a lot of other groups but Blaine Bettinger is truly an expert in this and the author of that book I recommended is a member of this group.

https://www.facebook.com/groups/geneticgenealogytipsandtechniques/

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I have a number of instances where 3rd and 4th cousins married and had children.  I have 2 great grandmothers with the exact name because one was named from the other who was her great aunt.  So  I understand what you are finding.  Mine also come from my French heritage side because they were glass and crystal makers and you had to marry within the guild.  

The Catholic Church allowed 2nd cousins to marry and gave dispensations when they thought it made sense like after a plague or when a mother died leaving young children and the father needed a fast wife to be the new mother.  The new wife was often pulled from within the first wife's extended family.  Also isolated areas often have a lot of families marrying into each other over generations.  

In my experience what I see is that sometimes a match can appear closer than it is but that does not make working the the DNA wrong or unusable.  You just need to check back in the paper trail another couple of generations and viola you may find the link at a 3rd cousin or 4th cousin level that the dna says is a 1st cousin level.  Not a big deal.  Just a little adjustment.

Answer 4

Yes their is a chance it could happen it is not perfect. The farther back you go the higher chances it could happen.