Re: especially long matching DNA segment #dna

Michael Goldsmith <michaelg32@...>

In my own family, these situations seem to occur once in a while. They
present contradictory conclusions. Segments as long as 45cM or longer seem
to indicate an ancestor recent enough that recombinations haven't broken
down this large block. However, the absence of very much additional DNA
leads to a conclusion that there was plenty of time for the recombinations
to break down any measurable blocks. Where my relative was known to me, this
result has belonged to someone who was a 2nd cousin once removed or even
more distant. Why an unusually long block survives in a distant relative is
most likely due to statistical chance in a process generally thought to be
largely random. However, I wonder (without any evidence) whether some groups
of genes are harder to recombine than others. If some one has some knowledge
on this particular point, please share it.

Michael Goldsmith
Bedford, NH

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