This post is incomplete and doesn’t encapsulate everything I intended to write about, but I never got around to finishing it, so this will do for the time being as DNA Genealogy is becoming quite popular…
Well this is my attempt at explaining DNA Genealogy. These days it all makes sense to me but I remember it was a massive learning curve as I got my head around Haplogroups, Segments, Percentages, Genomes etc. I’m still learning new things about it even now and there are definitely a lot more people out there who really delve deep into it, but I will try and explain the basics to help you understand how it works and what you can expect.
There are currently 3 main DNA testing companies out there at the moment, that deal with the genealogy aspect of it. There are more but these 3 are the most well known. Ancestry.com; 23andme.com (autosomal test only) and FamilytreeDNA.com.
All have their pro’s, con’s and various price differences.
Most tests involve you spitting into a special tube or taking a cheek swab and sending it off to the company.
A quick lesson in DNA before we get into the nitty-gritty. Males inherit a Y chromosome from their father and a X chromosome from their mother. Females only inherit two X chromosomes from their mother.
All companies offer Y-DNA and mtDNA testing. So Y-DNA refers to the Y chromosome. Because females do not inherit a Y chromosome, only males can do this test which explores the direct paternal line. So if you are female you will need to get a blood brother, father, paternal or paternal grandfather/uncle/cousin, to offer a saliva sample for this test.
When it comes to exploring genealogy matches resulting from this test, generally speaking, if you find a match with the same surname as you (unless it’s a very common surname) there is a high probability that you share a mutual direct paternal ancestor at some point. If you do not share the same surname then it usually means that either it’s just a coincidence that you are matched OR there’s been a discrepancy along the way in that someone was adopted into the family or a female ancestor diddled with the milkman or historical equivalent. The test cannot confirm who and when so you would have to refer to other matches to triangulate where a discrepancy could have occurred. This can be quite time consuming.
FamilytreeDNA has surname projects on its website that you can join and compare your results with other people of the same surname.
Another thing to note with DNA is that it mutates over time. Some genes mutate at a faster rate than others so you will often find that surname pockets around the world will have similar mutations in the faster mutating genes.
Y-DNA tests come in different degrees of accuracy. The most basic is a 12 marker test, these 12 markers usually take a very long time to mutate. There are then 37, 67 and 111 marker tests. The higher the number the more marker results and the more you can match with others resulting in higher accuracy.
I personally wouldn’t bother with just the 12 marker test as any matches could be anywhere within approximately the past 30 generations (that’s nearly 1000 years). At least the 37 brings you to within 8 generations (still hard to trace), 67 around 6 generations (difficult but doable and 111 within a much easier 4 generations. If you can afford it and are conducting the test to help with genealogical roadblocks within the past 300 years then you’d want the 111 marker test.
When receiving the Y-DNA results you’ll get the amount of markers you bought, say 111. Each marker is called a STR: Short Tandem Repeat. Each marker is given a name, such as DYS393. Each marker has a numerical value, for example as 12. It’s these numbers that you use against each marker to determine your matches. The more that match, the more likely you have a shared ancestor. Faster mutating markers may show a 1 or 2 digit difference to your own results. Depending on the marker you can figure out how this affects the match’s accuracy. For example if on one particular marker, DYS393 you have 12 but a match has exactly the same in every other marker but 13 for DYS393 then that particular marker has only mutated once. If it’s 14, it’s mutated twice. This can also go the other way with 11, 10 etc. The higher the difference in the number, the more times it has mutated and as such, more generations would have passed. Websites are around showing the estimated rate of mutation for each marker. Some are likely to mutate every 4 generations, others may go through 20 generations before mutating.
But before you head into checking out your ancestral matches, you’ll probably see your Haplotype group. If you’re male you’ll have a paternal haplotype and a maternal one. This is inherited directly down each line. Females however will only have a maternal haplogroup as they do not receive the fathers Y chromosome.
So what is a Haplogroup? Well this refers to your ancient point of origin (prior to seal travel and colonization but also includes thousands of years ago.
When humans started migrating out of Africa they split off into groups as they wandered the earth and produced pockets of population resulting in everyone getting similar DNA sequences on the markers that rarely mutate.
The Haplogroups for Y-DNA are given a letter from A-T. The A’s and B’s are most likely to be of recent African descent, originating from populations who never left the continent. C’s are most likely to be of Asian, North American or Oceanic descent. F includes parts of Asia, Europe and South America and so on and so on.
Each Haplogroup then splits off into subclades of a more refined population group. Some can even be quite specific with R1b1c7 belonging to a 5th Century Irish King who fathered so many children that now around 90% of men in some pockets of north-west Ireland and Scotland have this same haplogroup and as such can trace this King as their ancestor.