Wednesday, March 24, 2021

Gina's Journey - Part 4: A Clue in the Chromosome Browser Comparison

DNA double helix
It was all too apparent, Gina and I had numerous crossovers between our ancestral lines and they all originated in the same endogamous community. There was one other tool at 23andMe that might offer an answer – the chromosome browser.

I navigated to “Advanced DNA Comparison” found under “Family and Friends” in the main menu and plugged in Gina’s name and the match that shared the same surname of our possible third great-grandmother, then clicked “Compare”.

If all three matches were descendants of the same ancestor, at least one segment of overlapping DNA should show up in the chromosome browser. At the top of the page it stated I shared 82 cMs with Gina and a bit more with our other cousin match at 104 cMs. Let’s call this cousin Debra. The results were neatly illustrated with bars for each of our twenty-two chromosomes plus X, being the 23rd chromosome. Gina’s shared DNA with me was color-coded in purple and Debra’s in orange. I shared DNA on five segments with Gina and on seven segments with Debra. But the three of us shared just 13.45 cMs together - all on one segment.

I had hoped for a bit more DNA shared between the three of us, but this amount did fall within the range of 4th, 5th or 6th cousins, and of course there were many in-between variations such as 5th cousin, once removed and so on (see DNA Painter – SharedcM Project for a full range of relationships based on shared cMs). This was an exciting discovery and a good triangulation match, pointing to a specific family line I had already documented in my genealogy research. Without directly accessing Gina’s DNA results or sorting through her matches, I had found a major clue to her paternal line using triangulation.


DNA double helix



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