Borland Genetics

I have a match on Ancestry and it says we don’t share any matches.   How could that be? I see this question come up several times a month in the various Facebook genealogy groups.   Well, there are four scenarios that can give rise to this situation, so let’s go through each of them. 1.       Ancestry sets a threshold of 20 cM for displaying shared matches.   That is, the shared match would have to share at least 20 cM with you and 20 cM with your match to be displayed as a shared match.   So if you’re down in the weeds of your matches and looking to find shared matches with donors who only match you at 10 cM, it’s possible you might find some, but what’s also pretty likely is that the segment that you inherited from your common ancestor is smaller than 20 cM, and while there may be many donors that match both you and your match on that segment, none of them match you at 20 cM (and most probably don't match your match to that...

Is It Possible That I Share No DNA With My Full Sibling? Whenever someone asks whether it’s possible that two siblings can share no DNA segments in common, it conjures up memories of watching the movie “Twins” back in 1988 where one sibling played by Arnold Schwarzenegger inherited all of the “good genes” of his parents, and the other played by Danny DeVito inherited all the “useless genetic material” (quoting the movie).  Most of the time, when I see a question on this topic in the Facebook groups, I see a lot of links to the famous genetic genealogy green chart (which provides observed cM ranges of different classes of relatives) and to DNA Painter’s tool (which provides the possibility of different relationships based on a given cM value), as well as a chorus of people shouting “DNA doesn’t lie!” (not my favorite expression, but that’s a topic for a different day).  Of course, both the green chart and the DNA Painter tool will tell you right away that it is impossi...

Marcia, Marcia, Marcia! "My big sister Marcia matches me at 3600 cM, and all this time I never knew she was my mother!!!  Now I know why she always treated me like a child!" When I see a post like this in one of the Facebook Groups (and I actually see it quite frequently), I always take a minute to stop and read the comments, because jumping to this conclusion is usually the result of one of two common genetic genealogy pitfalls, both of which often lead beginner genetic genealogists down a rabbit hole.  Furthermore, when the sibling that comes in at around 3600 cM is an older brother, I frequently see comments responding to the post by well-meaning beginners, insisting that the only conclusion is that the brother must have committed some act of incest resulted in the birth of the individual who made the post (the original poster in FB terminology).  Needless to say, these types of conclusions can lead to serious family conflicts and permanent damage to family r...

What's the Difference Between Build 36 and Build 37, and Should I Care? To even begin to tackle this problem, we’re going to first need to understand what a “build” is.   Perhaps you may have seen references to “build 36” or “build 37” on FTDNA or GEDmatch or Borland Genetics, or to “build 38” on SNPedia.   Never heard of SNPedia?   We’ll cover that in future editions in this blog.   But to get to the point, when you hear these terms, we are referring to sequential versions of the accepted map of the human genome by the scientific community (or a dedicated group of scientists thereof known as the Genome Reference Consortium).   Each build represents a refined understanding of the sequence of base pairs along our chromosomes. A loose analogy to build versions would be the sequential editions of the Rand McNally road atlas, but with one major difference.   When Rand McNally publishes subsequent editions of its atlas, it generally does so becaus...

Why You Should Merge Your Factory DNA Kits:   SNP Overlap Demystified In this blog, I want to briefly discuss why it is best practice to merge your factory kits from different testing companies prior to working with third party raw DNA tools such as Borland Genetics or GEDmatch.   By factory kits, I simply mean raw DNA data files that were created directly by the testing companies by processing actual DNA samples. The first concept to understand is that different testing companies sample different sets of data points along your chromosomes.   We refer to the totality of the data points sampled in a single DNA kit that kit’s “template.”   Furthermore, individual testing companies have changed their chips over the years, also resulting in different kit templates.   When you hear people talking about an Ancestry v1 or Ancestry v2 or 23 & Me v4 kit, they are referring to their tests by their template revision version.   The ISOGG Wiki does...

If I match Cousin A and Cousin B on chromosome 6, does that mean that we share a common ancestor? The answer is a bit complicated! First, the general answer: General rule:  If you and cousin A and cousin B all match across a significantly overlapping span of the same copy of the same chromosome (called a segment), it is highly probable that you do so because the three of you all inherited that segment from a common ancestor. But what does that mean? First qualification :  It's not enough that the matches both match you on the same chromosome.  The matches must also match you over the same span of that chromosome.  Position on a chromosome is generally measured in MBP or Mega-Base-Pairs.  If Cousin A matches you on chromosome 6, but over the span of 23 MBP to 51 MBP, but Cousin B matches you over the span of 63 MBP to 81 MBP, this is not evidence that you and both matches share a common ancestor because these are segments to do not overlap....