I've always cast my 'DNA Net' wide because I am trying to find matches to distant cousins, but a few weeks ago something happened that I had not noticed before.
My other siblings have tested and it is not unusual to find a match that only matches one of us. I've come to expect that. But last week a match from Company A DID NOT MATCH ME AT ALL ON COMPANY B'S SITE. That has NEVER happened to me. So, I compared several of the matches and this is what I found.
Matches to me:
PR shares 29.2 cMs on one segment at company A. Not a match at company B.
CB shares 27.6 cMs on one segment at company A and only 21.93 at company B.
CP shares 47.1 cMs on one segment at company A and only 22.55 at company B.
SB shares 37.16 cMs on one segment at company A and only 16.99 at company B.
The match difference to CB was not enough to alarm me, but I wanted to know why PR was not a match at all at company B and the others were roughly half. These are all matches on the same chromosome and are the only segments the testers match on. They are also all well-proven cousins to a single family. All the locations reported overlapped with each other.
The difference between the match analysis was with the SNPs reported. Company B reported on roughly half of the number of SNPs that company A reported. The first match, PR, was the lowest number of SNPs reported at company A, so I can only speculate that the total number was below a reporting threshold at company B.
This experience reminded me of two things - SNPs matter and if cMs shared do not seem 'right', check with another company.
If I was only working with Company B, I would not have found this important distant cousin! PR's match placed a previously known, but unconnected group onto my tree and helped me find three other distant cousins!
Cast your DNA net wide!