I don't understand a GEDmatch result that looks like a match - Scottish DNA

[janicejo]

I'm trying to confirm that one of my father-in-law (Dad)'s DNA matches (Jane) is related to him at her 2g grandfather. Dad's own great-grandfather was never named to his grandfather (b. 1850, Fife). Jane's 2gg and Dad's great-grandmother were from the same parish (Kilconquhar).  Just this week Dad got NEW DNA hit with the same surname as Jane's 2gg. New DNA hit kindly assented to put his DNA into GEDmatch, and its a beautiful sight: Dads, Jane's, and New guys all over-lapping each other on Chromosome 1.  This is Jane's smaller piece of matching DNA to Dad, the main one is 30 cM, so we are sure Dad and Jane match. Jane's smaller piece, the one on Chr 1, is 6.5 cM long.  So I think there should be 6.5 cM of matching with New guy.  But GEDmatch says only 3.1 cM.
       How can this be? Because it can't be the other chromosome, because Dad's mother was Finnish, and I'm sure if I spend 10 minutes on GEDmatch I can find his corresponding Finnish match.   (The Finnish people are big genealogy and DNA enthusiasts, and they are so nice and helpful). 
       So can anyone explain why GEDmatch says 3.1 when I can see 6.5? Janice

[Alexandrina]

The autosomal DNA re-combines with every conception so even siblings can have varying results. Also , don't forget the chromosome is doubled with sections representing your maternal side and paternal sides from your parents with  many portions recombining . Some segments however are transmitted intact from generation to generation and it is these segments that one hopes to find via autosomal testing .

Alexandrina Murray
Murray Clan DNA Research Project.

[janicejo]

Thank you ALexandrina.  I re-read my post, and I see exactly what you mean.  I've read extensively on GEDmatch's workings, and I'm much better at finding matches for my father-in-law, on both his Scottish and his Finnish side.
   One of his close relatives (3rd cousin) served in WW1 in the 4th regiment of the South Africa Infantry.  Their colors were the MURRAY TARTAN!!  I just got a picture of the regiment in their kilts performing a "war dance" in France in 1918.  If you would like a copy, PM me. Janice


(My family - Scotland: (Aberdeenshire and Perthshire): Johnston, Booth, Sangster, Duncan, Smith, Ledingham, Leslie, Taviotdale, Hall)  England: (Staffordsh., Warwicksh., Worchestersh., who know where): Giles, Wills, Atkins, Roberts, Riley (English Romany), Sillitoe, Meriden, Bealand)
(Husband's family - Scotland:(Fife): Wallace, Rodger, Robertson, Finlay, Bennet, Ballingall, Kirkcaldie, Kinsman, Udny, Wilkie)