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Old 13th February 2017, 04:00 PM
ArthurO ArthurO is offline
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Join Date: Apr 2013
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Visual Phasing of Three Siblings

I have been trying the Visual Phasing of Three Siblings methodology outlined by Kathy Johnston (http://forums.familytreedna.com/show...visual+phasing) and promoted by Blaine Bettingr (http://thegeneticgenealogist.com/201...e-part-1-of-5/). While I follow and understand the methodology, I am having problems determining where some recombination events occurred and to whom they should be attributed.

The three siblings are myself (A - GEDMatch T511436 ), my sister (B - T028821 ) and brother (J - T517283 ). The attached file illustrate these problems. The first file (Visual Phasing chr 6.jpg) is my attempt to phase chr 6. My questions are:
- are the re-combinations events identified by the " J J " right under the 6 in the title and " B " at the end of the chromosome valid? Each shows as about 850 SMPs, but I not sure that matters.
- what do I do with the mess within the red ellipse. There are three segments that end or begin within a short length. See second file (Visual Phasing chr 6 HR,jpg) for this area from GEDMatch's 1-1 high resolution display. If each of these are re-combination events, to whom (A, B or J) should they be attributed?
It's a great technique, but it seems are none of my chromosomes want to make it easy for me!
TIA, Arthur
Attached Images
File Type: jpg Visual Phasing Chr 6.jpg (64.4 KB, 25 views)
File Type: jpg Visual Phasing Chr 6 HR.jpg (47.7 KB, 14 views)
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Old 17th March 2017, 09:26 AM
DaveInGreece DaveInGreece is offline
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Sometimes the only way to see what's really happening is to add data from known cousins (or even from strangers). I've seen cases where a person has crossovers on the paternal and maternal chromsome at almost exactly the same spot, or where two siblings have a crossover at almost exactly the same spot. Anomalous events like that can't be revealed purely by visual phasing of three siblings: you need data from other people.
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Old 17th March 2017, 10:19 AM
ArthurO ArthurO is offline
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Join Date: Apr 2013
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I am trying to identify matches that fit into the various segments. However, the many inter-marriages in the 1800s on my mother's side makes identifying a match unique to one side or the other difficult. My father, with a mother of Swedish ancestry and father with British Isles ancestry, is much easier to find the matches for each segment.
Thanks for your comments and advice. It seems that trial and error may be the only way to identify the crossover points in some cases.
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