From Father To Son
Debbie Kennett explains how you can use a Y-DNA test to trace your male line back to the Middle Ages
The first Y-chromosome DNA (Y-DNA) tests came onto the market nearly 20 years ago, but the focus in recent years has been on autosomal DNA (atDNA) testing – the type of test offered by AncestryDNA and other companies that gives you matches with genetic cousins who could be related to you on any of your ancestral lines. As a result Y-DNA testing has taken a back seat, but it is still a very important tool for the family historian and something with which everyone should become familiar. While atDNA is useful for answering questions about relatedness within the last five or six generations, it cannot be reliably used for matches with distant cousins because of the way it is shuffled up and diluted with each new generation. The Y-chromosome, in contrast, is passed on virtually unchanged from father to son, which makes it a useful tool for answering questions about relatedness on the direct male line (the patriline) going back to the beginning of genealogical records in medieval times. It can also be used as a complement to atDNA testing. The big limitation is that only males have a Y-chromosome, so the test can only be taken by men. If you’re a female you’ll need to find a male relative, such as your father, brother or cousin, to take a Y-DNA test on your behalf.
As with all DNA tests, it is
‘It is important to combine Y-DNA results with genealogy’
important to combine Y-DNA results with genealogical research. A DNA test on its own provides very little useful information, and the power of the test lies in the ability to compare results in a matching database. FamilyTreeDNA (FTDNA) dominates the market for Y-DNA testing, and is now the only company that has a Y-DNA matching database. If you’ve tested with 23andMe or Living DNA then you will receive information about your Y-DNA
haplogroup (your branch on the Y-DNA tree – see the box below). While these reports can be very interesting, they relate to your deep ancestry thousands of years ago, and cannot be used for genealogical matching.
How To Use Y-DNA Testing
In most cultures Y-DNA tracks the same line of inheritance as surnames. A Y-DNA test can be used to answer questions such as whether two men with the same surname from different parts of the country share a common ancestor, or whether two variant spellings of a surname have a common root. You will get the most out of a Y-DNA test if there is already a structured project for your surname. If you’re the first person with your surname to test then you are not likely to get much from your results, but if there is a well-established project you are more likely to have a useful match. Even if you don’t, your results will still contribute to the knowledge of the surname.
Y-DNA testing can also be used in unknownparentage searches. For example, if someone was adopted or donorconceived, or if the patrilineal ancestor was illegitimate and the father’s name was not given on the birth certificate. In these situations you are relying on the power of the matching database, and you are hoping for close matches that will provide clues to the biological surname of the
‘You will get the most out of your test if there is a project for your surname’
father. Some people get answers straight away, while in other cases people have to wait for many years for the right match to come along. I have some examples in my Devon DNA Project ( familytreedna.com/groups/devon) where testers had an illegitimate ancestor and had a match with another person with a different surname whose ancestor had lived in the same village. This provided a strong clue to follow up in the genealogical records.
Another important reason for testing is to ‘biobank’ your Y-DNA profile. It may be that there is not a project for your surname but you are the last person in your family with the surname because you have no male descendants. Adding your DNA to the database will help future researchers as and when a surname project is set up. FTDNA allows you to nominate a beneficiary for your account. This could be a friend or relative, or it could be a project administrator.
What Is Tested?
There are two different types of marker that are tested – short tandem repeats (STRs) and single-nucleotide polymorphisms (SNPs). STRs are short repeating sequences of DNA letters. The number of repeats is counted up,