Author Topic: Troublesome segment of DNA  (Read 500 times)

Offline Garen

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Troublesome segment of DNA
« on: Monday 01 June 20 12:35 BST (UK) »
I wonder if anyone has any ideas on this problem ...

I have three DNA kits on MyHeritage (all imported from Ancestry) - myself, my Dad and my Aunt (my Dad's sister).

We all match 'HRC' on chr 4 - and I know the common ancestor (paternal-Cameron, Perthshire) and I have put HRC's data into my DNAPainter chart.

Recently I came across a new match, 'KW' and I know the common ancestor (paternal-Blyth, Fife). I went to add her data into my DNAPainter chart and saw that KW's data covers the same segment as HRC, yet the common ancestors (Blyth for KW and Cameron for HRC) are not related.

The obvious conclusion - I guess - is that either HRC also has previously unknown Blyth ancestry as well as the known Cameron, or KW has previously unknown Cameron ancestry as well as the known Blyth.

My (paternal) Aunt matches both HRC and KW in the same segment on chr 4. The problem is my Dad matches HRC on chr 4, but KW does not come up as a match for him. Yet, surely all my paternal DNA comes from my Dad, so if I match KW on chr 4 (and so does my Aunt, his sister) - then why doesn't my Dad?

When I use the MyHeritage chromosome browser to check myself, HRC and KW, chr 4 comes up as a triangulated segment. When I check my Aunt, HRC and KW, chr 4 comes up as a triangulated segment. My Dad matches HRC on chr 4, but KW is not a match. When I compare everyone together: me, my Dad, my aunt and HRC and KW; the browswer says 'no triangulated segments'.

I match my aunt on this segment 67 cM, HRC 14 cM, and KW 17 cM. And my Dad, unsurprisingly, 100% (see graphic).

Hope I haven't lost you - does that make sense?

I've researched some of the lines both HRC and KW don't have recorded on their trees, and, so far, there is no sign of either having the other's family on it, with no geographical places in common either (though I can still try and go back further).

Any ideas or theories welcome! Thank you -
Garen

Second Anglo-Afghan War 1878-80 - http://www.angloafghanwar.info
Family research - http://www.garenewing.co.uk/family/

Offline Craclyn

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Re: Troublesome segment of DNA
« Reply #1 on: Monday 01 June 20 20:07 BST (UK) »
The diagram you have attached looks as though it is showing overlapping segments of DNA, but not triangulation. There would be a box around any triangulated segments. Some of those could be from your paternal side and some from your maternal side.
Crackett, Cracket, Webb, Turner, Henderson, Murray, Carr, Stavers, Thornton, Oliver, Davis, Hall, Anderson, Atknin, Austin, Bainbridge, Beach, Bullman, Charlton, Chator, Corbett, Corsall, Coxon, Davis, Dinnin, Dow, Farside, Fitton, Garden, Geddes, Gowans, Harmsworth, Hedderweek, Heron, Hedley, Hunter, Ironside, Jameson, Johnson, Laidler, Leck, Mason, Miller, Milne, Nesbitt, Newton, Parkinson, Piery, Prudow, Reay, Reed, Read, Reid, Robinson, Ruddiman, Smith, Tait, Thompson, Watson, Wilson, Youn

Offline Garen

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Re: Troublesome segment of DNA
« Reply #2 on: Monday 01 June 20 21:44 BST (UK) »
Thanks very much for your thoughts, Craclyn - really appreciate it.

Although I don't have my mother's DNA tested, I do have a maternal aunt's kit up on MyHeritage as well, and she doesn't match with KW (not definitive, I know).

But the fact that I match my paternal aunt on that segment, and we both match KW on that segment (and it comes up as triangulated when it's us 3 together), but that my Dad does not match - just doesn't make any sense.
Second Anglo-Afghan War 1878-80 - http://www.angloafghanwar.info
Family research - http://www.garenewing.co.uk/family/


Offline Craclyn

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Re: Troublesome segment of DNA
« Reply #3 on: Monday 01 June 20 23:23 BST (UK) »
Are your father and your paternal aunt full siblings?
Crackett, Cracket, Webb, Turner, Henderson, Murray, Carr, Stavers, Thornton, Oliver, Davis, Hall, Anderson, Atknin, Austin, Bainbridge, Beach, Bullman, Charlton, Chator, Corbett, Corsall, Coxon, Davis, Dinnin, Dow, Farside, Fitton, Garden, Geddes, Gowans, Harmsworth, Hedderweek, Heron, Hedley, Hunter, Ironside, Jameson, Johnson, Laidler, Leck, Mason, Miller, Milne, Nesbitt, Newton, Parkinson, Piery, Prudow, Reay, Reed, Read, Reid, Robinson, Ruddiman, Smith, Tait, Thompson, Watson, Wilson, Youn

Offline Garen

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Re: Troublesome segment of DNA
« Reply #4 on: Tuesday 02 June 20 01:00 BST (UK) »
Yes - I believe so, and 2,800 cM shared seems to confirm that (just about 40%).
Second Anglo-Afghan War 1878-80 - http://www.angloafghanwar.info
Family research - http://www.garenewing.co.uk/family/

Offline rlw254

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Re: Troublesome segment of DNA
« Reply #5 on: Tuesday 02 June 20 01:13 BST (UK) »
I suspect the match for your father is under the threshold used to determine a 'match'. If you were to analyze the two kits on GEDmatch where you can lower this figure you might see some overlap. SNP density could likely allow you to be a match with this person and not him.

Offline Garen

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Re: Troublesome segment of DNA
« Reply #6 on: Tuesday 02 June 20 10:43 BST (UK) »
Thank you for looking at this, rlw254.

I'm not sure I understand the concept of SNP density and how it would affect this. While I'm fairly certain HRC and KW aren't on GEDMatch (I'm going to contact KW later today), when I look at various combinations of me and my Dad and Aunt on GEDMatch it all seems to be a pretty solid match in that segment (the 83,000,000 - 111,000000 area). I've attached another image! :-)

I match HRC on chr 4 at 93,927,040 - 111,685,081*
My Dad matches HRC on chr 4 at 94,775,266 - 111,416,282
My Aunt matches HRC on chr 4 at 95,690,975 - 111,416,282

I match KW on chr 4 at 85,360,873 - 108,206,062
My Aunt matches KW on chr 4 at 85,360,873 - 109,180,551

Thanks again for working through my complicated message!

Best - Garen

* Edit: I actually think I uploaded my 23andMe kit to MyHeritage, but it's my Dad and Aunt's Ancestry kits.
Second Anglo-Afghan War 1878-80 - http://www.angloafghanwar.info
Family research - http://www.garenewing.co.uk/family/

Offline Garen

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Re: Troublesome segment of DNA
« Reply #7 on: Tuesday 02 June 20 15:17 BST (UK) »
Here's another interesting thing ...

As I said, my Dad doesn't match KW, but both my paternal Aunt and I do (see above). One of KW's top matches is MH - a possible 2nd cousin (138 cM match).

My Dad does match MH on chr 4: 98,710,962 - 109,411,079 (7.9 cM)
I match MH on chr 4: 85,008,082 - 109,987,288 (19.6 cM) (and triangulates with KW)

My Aunt doesn't come up as a match with MH ...

I feel that this is a logic puzzle to which I'm not seeing the obvious answer (never had a maths brain).

Second Anglo-Afghan War 1878-80 - http://www.angloafghanwar.info
Family research - http://www.garenewing.co.uk/family/

Offline Carmella

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Re: Troublesome segment of DNA
« Reply #8 on: Tuesday 02 June 20 15:47 BST (UK) »
Hi,

I have a several matches (0.4-0.5%) on MyHeritage who do not match my father or mother's kits at all.

I also have several matches with whom I share 0.4 - 0.5 % DNA but my parent only has 0.2 shared DNA.

After searching online for an explanation to this, the best reason I could find is that it is down to imputation which MyHeritage uses on upload kits - which all of mine are.

https://dna-explained.com/2017/09/05/concepts-imputation/

I don't know whether this applies in your case as in mine they were smaller segments, but I've only found this with MyHeritage matches and not with other companies. (However I did effectively get a free DNA test so I can't really complain!)