What is genetic genealogy?

Written by Ellen Hinkley
28 February 2017

Genealogy is the study of family history and often involves building a family tree. Using DNA testing to research your family history is known as genetic genealogy, and it’s a great way of understanding your genetic heritage. The DNA tests most commonly used for genealogy come with tools to help you identify and connect with your living relatives, and features that facilitate the building of your family tree.

Depending on the type of DNA that you test (autosomal, Y DNA or mitochondrial), these so-called ‘Family Finder’ tools can identify whether the relatives you find are related to you on your mother or your father’s side of the family. Because of this, they can also be helpful for confirming relationships identified using traditional genealogical methods.

If you’re interested in studying your family history, genealogy DNA tests are a popular way of overcoming roadblocks in your family tree research. In addition, if you’re lucky enough to be related to another genealogy enthusiast, you might just be able to merge your family trees to reveal a huge swathe of family you never knew you had!

If you’d like to expand your research with a genealogy DNA test, take a look at our list of ancestry testing providers.

What is autosomal DNA and how is it used for genetic genealogy?

Autosomal DNA testing is one type of genetic analysis that can be used for genealogy research. These types of test analyse the DNA that is inherited from both parents, and which is organised into autosomes – a specific type of chromosome.

Although autosomal DNA can be used to find family, there’s no way to determine which autosomes or autosomal segments you’ve inherited from which parent. Therefore, it can be difficult to work out how to add these individuals to your family tree, if you’re not able to establish how you’re related to them using traditional methods.

Another important point to make is that half of your autosomal DNA is inherited from each parent, which is therefore a quarter from each grandparent, an eighth from each great-grandparent, and so on. Because of this, it becomes more difficult to accurately identify those relatives who share an ancestor with you according to your autosomal DNA the further back you go. It’s widely accepted that the living relatives identified by any Family Finder tools according to your autosomal DNA will not share an ancestor with you any further back than five generations ago.

Family Finder tools that use autosomal DNA
As discussed, Family Finder tools will match you with individuals who share sections of your DNA, providing those people are also customers of the same company that you’ve bought your DNA test from (e.g. 23andMe).

The proportion of DNA that you share with someone allows genealogy DNA testing companies to estimate the level to which you are related, ranging from sibling to distant cousin. These matches are usually listed in terms of how much DNA you share, with the closest relatives at the top and the most distantly related at the bottom. Most people will see a long list of matches when they first use a Family Finder tool, the majority of which are cousins.

For those who are specifically looking for their immediate biological family (e.g. adoptees), the Family Finder tool can serve as a way of connecting with those relatives. Something that’s important to be aware of is that the relatives you find may not be what you expect, and there is a chance that using this feature may reveal upsetting information for all involved. If you’re looking for immediate biological family and you think this might happen, we recommend you speak with a genetic counsellor first, who will be able to answer any questions you have about the testing process and what the implications may be.

It’s also worth noting that several of these matches will be fourth or even more distantly related cousins. You’re unlikely to share enough DNA with these ‘relatives’ to be able to link them to your family tree, but it may be interesting to see who you’re distantly related to and where in the world they live. Many genealogy DNA testing companies that offer a Family Finder service will allow you to change the threshold, meaning that you can filter out matches that are not close relatives.

How the Family Finder feature works
To compare the segments of autosomal DNA that you share with others in a database, companies will use several tools to interpret the basic raw data that they obtain from your DNA sample. This raw data won’t include the full sequence of your DNA, but a selection of relevant genetic markers – these are small differences in our genes that account for the genetic variation between humans, and they can be used to make conclusions about your ancestry.

The most common markers used are genetic variants (also known as SNPs). Most ancestry companies use specialised chips which allow them to look for between 600,000 and 1,000,000 genetic variants in your autosomal DNA, commonly finding about 100,000. These can then be compared with the variants possessed by other customers on their database, to calculate how closely you’re related to them.

In addition to helping you to find family, the genetic variants in your autosomal DNA can be used to provide you with information about your genetic ethnicity, which is discussed further in our article: What is an ethnicity DNA test?

What is Y DNA and how is it used for genetic genealogy?

Another type of DNA that can be analysed to research your genetic genealogy is Y DNA. This is the DNA that males inherit directly from their fathers and it can be used to trace back many generations of your paternal lineage. Women don’t possess this DNA, but can have a paternally related relative, such as a father or brother take the test for them. You can read more about the other features of Y DNA tests and how they work in our article: What is a Y DNA test?

Family Finder tools that use Y DNA
Family finder tools that use Y DNA are much less common than those that use autosomal DNA. One of the biggest providers of Y DNA tests is Family Tree DNA, and this is one of the few companies that run a Family Finder service based on Y DNA test results. Y DNA Family Finder services will list the living relatives that have been identified on your father’s side of the family, by looking for shared sections of Y DNA, or according to your ‘paternal haplogroup’ – a group of individuals who all share a common paternal ancestor according to shared genetic markers.

Some companies (iGENEA and The Genealogist for example) resell Family Tree DNA’s tests, and not all resellers will give you full access to Family Tree DNA’s features (including their Family Finder service). Therefore, if this feature is important to you, you should buy directly from Family Tree DNA or check with the reseller first.

Family Finder tools that use Y DNA are slightly different to those using autosomal DNA. This is because living relatives will be identified according to a second type of genetic marker known as Short Tandem Repeats (STRs) instead of SNPs. Where SNPs are identified according to specialised chips (discussed above), STRs are revealed by using a combination of amplification, gel electrophoresis, and dyes/staining. For example, when taking a Y DNA test with Family Tree DNA, they’ll look for between 16 and 111 STR markers depending on the level of accuracy you’re looking for.

Just like a Family Finder tool that uses autosomal DNA, many genealogy DNA testing companies will allow you to change the matching threshold (in this case, the number of shared STRs in your Y DNA), meaning you can filter out individuals who are not close relatives, or view those who only share a very ancient ancestor with you.

Surname projects
Surname projects allow those with the same (or a similar) surname to communicate with each other and share Y DNA results. These projects are normally administered by volunteers, and they’re a great way to add to your family tree.

If you have a rare surname and you identify a distant relative who’s taken Y DNA test with a different company to you, a surname project will help you to compare your records to establish your relationship. Alternatively, you may have a popular surname and you’ve identified individuals who share it but who aren’t being matched to you according to your Y DNA. In these cases, a surname project will help you work out whether you should persevere in trying to match with these individuals genetically, or if it’s unlikely that you’re related to them and should focus elsewhere.

You may be surprised to find that not everyone within each group has exactly the same surname. They are all likely to share the same origins, but their families have probably adapted their surnames over time into many different variants. You may even be able to work together to discover the original version of your surname, as well as to learn more about your shared ancestors and origins. Family Tree DNA hosts many of these projects which number in the tens of thousands.

What is mitochondrial DNA and how is it used for genetic genealogy?

Mitochondrial DNA (aka mtDNA) testing is similar to Y DNA testing in terms of how it can be used to research your genealogy. The major difference is that mitochondrial DNA is passed directly from mother to child (of either gender) rather than from father to son. Both males and females inherit this DNA and therefore both genders can take this type of test to find out about their maternal lineage. You can read more about the other uses of mitochondrial tests in our article: What is a mitochondrial DNA test?

As with Y DNA tests, Family Tree DNA and some of its resellers are the only companies that offer a Family Finder feature to match relatives based on their mitochondrial DNA. As well as identifying living relatives according to the proportion of mitochondrial DNA that is shared, matches are listed according to your ‘maternal haplogroup’. Similarly to paternal haplogroups, your maternal haplogroup is also designated on the basis of shared genetic markers.

What is traditional genealogy and how does it relate to genetic genealogy?

Those who have carried out any sort of traditional genealogy will know that it often involves trawling through records, including birth and death certificates, census records, newspaper clippings and more. The advantage of this sort of research is that it can give you a real insight into the lives that your family members led. However, traditional genealogy often turns up anomalies, and missing information and uncertainty is common.

Traditional and genetic genealogy research can often be used to complement each other to help you trace your ancestry. For example, reaching a dead-end while searching through census records may prompt you to test your mitochondrial DNA, and find a number of living relatives on your mother’s side of the family who hadn’t appeared in the census data. Conversely, if you find a 3rd cousin after taking a genealogy DNA test, you may not be able to place them on your family tree without identifying that person and their parents in the census records.

Combining traditional and genetic genealogy
Some DNA genealogy providers (MyHeritage and AncestryDNA for example), allow you to use their Family Finder service in combination with traditional genealogy. They maintain both a database of their customers according to DNA results, and hold a catalogue of birth, marriage and death records, newspaper articles, and other historical records that you can search.

To help you combine these different arms of genealogical research, many companies will make it easy for you to blend the two types of results together in their online interfaces. For example, AncestryDNA will let you build your family tree within their online interface, and after you’ve added what you know, you can incorporate the relatives you’ve found according to your DNA at the touch of a button. You can then look through the digitised historical records in AncestryDNA’s interface, and attach them to the individuals on your tree so far. AncestryDNA will then give you hints about other potential relatives that you can investigate, according to the blend of research you’ve already conducted.

Something to be aware of however, is that these companies often require you to pay a subscription fee for ongoing access to the historical records they hold, in addition to the cost of the genealogical DNA test!

Top tips for connecting with relatives

To get the most from your DNA genealogy test, whichever type of DNA you have tested, there are some dos and don’ts to be aware of in order to maximise the amount of genealogical information you can obtain. The main thing to keep in mind is that the more you’re willing to share, the more that the living relatives you identify will be willing to share with you. Making your profile as complete as possible, not just in terms of sharing your ancestry, is also a good way to encourage connections. Adding a picture and a bio will help to personalise your profile, and will make you more approachable.

Something else worth noting is that some of your matches may need a little time and consideration before deciding whether to share their personal information with you. Therefore, don’t worry if you don’t receive responses straight away, and try not to contact them more than a couple of times if they don’t respond!