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9

I think the prior answers are either misleading or wrong, and people should not miss out on the opportunity to get great DNA information because they were discouraged by those answers. If you have the DNA for Charlie (the parent), and any of Charlie's children (Dick, Elizabeth, Frank, and George), you can at least partially phase a child (and thus pseudo-...


6

Edit: Brainstorm and I had an extended discussion through the comments on whether Visual Phasing of siblings can add information that the parent's DNA test doesn't already add. I have been convinced that yes, doing so can provide information not had by the parent alone. It is possible to phase the parents from the children with the additional help of ...


6

I will try to explain more comprehensively. What does phasing do and what task does it solve? We use phasing to separate the list of matches of one's person into two smaller lists of probable relatives: by paternal and maternal lines. Also phasing is great in terms of eliminating IBS (non-IBD) matches. Imagine that somebody has small DNA overlap with your ...


4

The simplest and most likely cause of the lack of a match is that Alice is related to Bob and Charlie through different parents. If Alice inherited the 36 cM of DNA she shares with Bob from, say, her father, and Alice inherited the 82 cM she shares with Charlie from her mother, then there would be no reason to expect any matching between Bob and Charlie. ...


3

GEDmatch does not disclose its methodology for phasing at GEDmatch Genesis. But if you and your mother tested at different companies, especially different companies that use different chips, then it could be that GEDmatch Genesis only includes SNPs that it can phase that are in both sets of raw data. ISOGG has an Autosomal SNP comparison chart which I'm ...


2

I have written an R library to do exactly what you are calling "grandparent-grandchild phasing". You can find the (open source) code at: https://github.com/castedo/genomology In addition to the R code, there are two PDF files on that page which show the math used in this software to estimate which segments of DNA come from which grandparent. I also run a ...


2

This can happen even with full siblings of the same parents. Each parent has a chromosome 18 from each of their respective parents (the grandparents). Let's call the father's pair 18pp (paternal-paternal), and 18pm (paternal maternal), and the mother's 18mp (maternal-paternal) and 18mm (maternal-maternal). Now imagine three children who inherit from each ...


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