An interesting BIFHSGO DNA meeting today on Zoom and the first I have attended for quite a while. Linda Reid presented a four generation study and it was most interesting. Nature will always take the simplest route so not surprised to see entire lengths of chromosome passing intact from mother to offspring or father to offspring. But the discussion reminded me that in pedigree collapse you do see one or more long length matches with third to fourth cousins that you would anticipate for a second cousin (or first) match. What you can not tell is whether that long length of chromosome is the result of fusing of similar lengths obtained from a common ancestor so that it looks like a single chromosome because it was inherited along the same path.
I really prefer DNA Painter because four of my five siblings have tested at 23 and Me so I have that nice pictorial image to work with when I am looking at cross-over points where I know that we either are completely identical or half identical or do not share any DNA for particular length. I can then work the fifth person in fairly readily as I have all five on FT DNA (and My Heritage) and four on Ancestry and Living DNA.
Lectures given on personal family work are excellent additions to the DNA meetings and thank you to Linda Reid for sharing.
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