There were 2745 pairs that were no-calls in 23andme, but were homologous in AncestryDNA There were 2320 pairs that were no-call in AncestryDNA, but were homologous in 23andme David From: Ann Turner [mailto:dnacousins@gmail.com] Sent: Thursday, December 17, 2015 3:32 PM To: David Schroeder; DNA Genealogy Mailing List Subject: Re: [DNA] My Raw Data Files - Comparison 23andme vs AncestryDNA GEDmatch "tokenizes" the data in an attempt to make it more uniform across platforms, so that should not be an issue for most SNPs. All C's are converted to G's and all A's are converted to T's (or maybe the opposite direction, but you get the idea). That fixes any strand orientation problems, but it introduces a few cases where the alternative alleles are also complementary base pairs in the double helix. The next effect of that is to give you a free ride for those few SNPs where you and your match are really opposite homozygotes. You speak of fixing errors -- I assume you're referring to no-calls rather that outright errors (miscalls). No-calls don't break up segments, just opposite homozygotes (e.g. CC in one party and TT in the other party). GEDmatch doesn't give any credit for the SNP threshold (although 23andMe and FTDNA do). For that reason, I predicted you might have a small increase in the number of matches, and I am puzzled as to why you saw a decrease. Ann Turner On Thu, Dec 17, 2015 at 11:39 AM, David Schroeder via <genealogy-dna@rootsweb.com> wrote: Kitty, I did flip the orientation as I noticed there were C-Gs and G-Cs on AncestrDNA files when I loaded them to a database. 23 only had C-Gs so I wanted it to look like 23 raw data. I see there is more to it than a simple ordering. I did not flip the orientation back when I recreated the fixed ANCDNA file. I wonder if that causes any issues? David