Wednesday, September 16, 2015

Autosomal Small Segment Triangulation HAM DNA Group #1

Small Segment Triangulation
HAM Y-DNA Group #1

The main purpose of the paper was to provide instructions that will permit viewing matching autosomal shared segments when FTDNA does not provide that information. Further, the intent is to help analyze a Y-DNA Group for matching shared autosomal segments by direct comparison between three or more people. This was written for those who had problems finding autosomal matches and who were also participants in the Y-DNA project. It is meant to help with a problem when the Y-DNA indicates that you should have a match, but the autosomal DNA indicates no match.

Screenshot of Autosomal Small Segment Triangulation

See also:

"Table 5 shows a typical set of alleles... These alleles (AA and CC) may indicate a Mediterranean ethnicity. The probability of a one to one match on this segment being a false positive calculates to be 1 in 7 quadrillion."

"Many 7 cM matches are SNP poor and under certain conditions will calculate as a false positive. There are many triangulated matches at 2.5 cM that confirm a relationship. Unfortunately, that relationship may be in the 7 to 14 generation range, making it difficult to determine the common ancestor. Triangulated small segment matching is very valuable in our research."
The process of genetic inheritance is often over simplified, leading consumers of genetic tests to believe that the amount of DNA from distant ancestors becomes negligible. In fact, segments of DNA pass down through the generations intact. Naturally occurring cleavage sites allow for small segments to exist at recurring chromosomal locations. These small segments can be used as familial markers in an autosomal haplotype.

Maximum-likelihood estimation of recent shared ancestry (ERSA)

Accurate estimation of recent shared ancestry is important for genetics, evolution, medicine, conservation biology, and forensics. Established methods estimate kinship accurately for first-degree through third-degree relatives. We demonstrate that chromosomal segments shared by two individuals due to identity by descent (IBD) provide much additional information about shared ancestry

A Study Utilizing Small Segment Matching

"Now that we understand IBS, IBD, Phasing and how matching actually works on a case by case basis, let’s look at applying those same matching and IBS vs IBD guidelines to small data segments as well."

4 Generation Inheritance Study

"There is a lot more information available to us in our DNA results than is first apparent.  It takes a bit of digging and you need to understand how autosomal DNA works in order to ferret out those secrets.  Don’t discount or ignore evidence because it’s more difficult to use – meaning small segments.  The very piece or breadcrumb you need to solve a long-standing mystery may indeed be right there waiting for you.  Learn how to use your DNA information effectively and accurately – including those small segments."

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