What DNA test should you take?

By Guest, 21 November 2018 - 1:51pm

Debbie Kennett explains how DNA testing can help with your family history research and how to choose the best test for you

Living DNA test
A Living DNA lab (Credit: Living DNA)

DNA testing has taken off in a big way in the past two years.

Get the full version of this article and much more family history advice in Who Do You Think You Are? Magazine December 2018, on sale now

Somewhere in the region of 20 million people have now been tested, with thousands added to the databases every day.

Even if you haven't yet taken the plunge, you will find that many of your relatives are already in the databases.

And all the companies have big sales in the run-up to Christmas, so now's the best time to start your journey.

However, a DNA test on its own is not very informative. It cannot tell you who you are or where you came from.

DNA testing is best used as a tool for your family history research in combination with documentary records. The power of genetic genealogy lies in the comparison process. You need to work with your matches in the databases, and compare family trees in order to identify a common ancestor.

DNA testing is also very useful for verifying your family history research. It can be very satisfying to have DNA evidence as additional confirmation of relationships.

However, you need to be prepared for a few surprises along the way. For this reason, when testing your relatives it's important to ensure that you gain their consent and warn about unexpected results. The Genetic Genealogy Standards Committee provide some useful guidance that you can download as a free PDF.

There are three different types of test - autosomal DNA, Y-chromosome DNA and mitochondrial DNA - all of which have specific applications. The choices of test will depend on the questions that you want to answer.

Historic family photograph DNA
A grandmother, mother and daughter in 1940s Devon (Credit: Keystone/Getty Images)

Autosomal DNA testing

The autosomal DNA test is now the most popular of the three tests and tests the autosomes from both parents.

These are the chromosomes other than the two sex chromosomes (X and Y) that contain most of our DNA sequences and genes.

We receive one set of 22 autosomes from our mother and one set of 22 autosomes from our father.

Before the DNA is passed on it is shuffled up in a process known as recombination.

The DNA we inherit from our parents is therefore a patchwork of DNA from all four of our grandparents.


Y-chromosome DNA (Y-DNA) is passed on by a father to his sons. The transmission usually follows the inheritance of surnames.

This test can therefore only be taken by males. Females will need to find a suitable candidate for testing such as their father, brother, uncle or cousin.

For genealogical purposes markers known as short tandem repeats (STRs) are tested. These are repeating sequences of DNA letters.

The number of repeats is added up, and for each marker you are given a number. Then your numbers are compared with the other people in the testing company's database.

You are given a list of the Y-DNA matches whose numbers most closely match yours. The 37-marker test is the standard entry-level test, but tests are also available with 67 and 111 markers.

Y-DNA testing can be used to verify existing research, to explore which different surname lineages are related and to investigate variant spellings.

Y-DNA test results are best co-ordinated within a structured surname project, where the results can be clustered into 'genetic families'.


Mitochondrial DNA

Mitochondrial DNA (mtDNA) is passed on by a mother to both her sons and daughters. Only females can pass on their mtDNA to the next generation.

An mtDNA test can therefore be taken by both males and females, and explores the direct maternal line, or 'matriline'.

However, it is not so easy to use mtDNA testing for genealogy because the surname changes with each generation.

Also, mtDNA mutates very slowly. Even if you have a very close match, the common ancestor might have lived 1,000 years ago - or more.

Nevertheless, mtDNA can be helpful when used with autosomal DNA testing to rule matches in or out on the matriline.

MyHeritage DNA test swab RootsTech
An attendee takes a MyHeritage DNA test at the RootsTech conference, February 2017 (Credit: George Frey/Bloomberg via Getty Images)


What DNA test should you take?


  • Has a useful chromosome browser view for the biogeographical ancestry test
  • Only company offering a report showing how much of your ancestry is shared with the Neanderthals
  • Interesting health and trait reports


  • Many of the people who test at 23andMe do so for health purposes, and don't opt in to relative matching




  • Market leader for autosomal DNA testing with the world's largest consumer DNA database
  • Easy-to-use interface with well-integrated family trees
  • Valuable features including Shared Ancestor hints and Shared Matches


  • Lack of chromosome browser and matching segment data are big disadvantages for advanced users interested in chromosome mapping




  • Market leader for both Y-DNA and mtDNA testing with the world's largest Y-DNA and mtDNA genealogical matching databases
  • Benefits from a wide variety of volunteer-run surname projects, haplogroup projects and geographical projects


  • Smaller autosomal database
  • Autosomal DNA-matching algorithms need updating to exclude false small segments


Living DNA (also available via Findmypast)


  • Ethnicity reports provide detailed regional breakdowns within the UK
  • Good choice if you want to keep your DNA data in Europe
  • Matching not ready at time of writing, but likely to be good for UK matches as the database grows


  • Smallest of the matching databases




  • Good coverage in most European countries, and provides support in 42 languages
  • Multilingual website should attract people from non-English-speaking countries, reaching markets poorly served by other companies


  • Limited tree-building and searching facilities with the free MyHeritage service 


Debbie Kennett is the author of DNA and Social Networking


Get the full version of this article and much more family history advice in Who Do You Think You Are? Magazine December 2018, on sale now

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