Posts tagged ‘23andMe’
Autosomal DNA is inherited by both males and females and received equally from each of our parents.
In commercial genetic genealogy tests our autosomal DNA is compared against a large database of others, looking for identical segments of inherited DNA that may indicate we have shared ancestors.
Some questions that might be answered by an autosomal test include:
- Can I find previously unknown cousins, solely from my DNA?
- Can I look for relatives on all branches of my pedigree (not just my father’s patrilineal or my mother’s matrilineal lines)?
- Can I test the accuracy of the family tree I have constructed?
How does it work?
Autosomal DNA tests examine 22 of the 23 pairs of chromosomes that we inherited from each of our parents. The remaining pair (called the ‘sex chromosomes’) determines gender. (X-chromosome analysis is often also reported in autosomal tests.)
We inherit about half our autosomal DNA (atDNA) from each of our parents and so about one quarter from each of our grandparents (and an eighth from each of our great grandparents…) – eventually we may not have enough DNA from a particular ancestor to be recognisable.
Close relatives share large segments of atDNA that each has inherited from a recent ancestor in common. More distant relatives may carry smaller sections of identical DNA. Commercial DNA testing companies predict the approximate relationship between genetic cousins based on the size and number of shared identical segments of autosomal DNA. (Very small pieces of atDNA in common are more likely to be coincidental rather than inherited.)
Because of randomness each time autosomal DNA is passed on, even siblings do not have identical autosomal DNA inherited from their parents and the amount of atDNA shared between relatives can vary greatly. As the amount inherited from a particular ancestor diminishes over the generations, eventually two distant cousins may not share enough DNA for a commercial test to identify them as genetic relatives.
While first and second cousins (and closer relationships) should be recognised in an autosomal test, and third cousins are extremely likely to be identified, only around half of fourth cousins will be found by their atDNA. By the time of fifth cousins, only about 10-15% will be recognised and by sixth cousins, only about 2-5% will be identified as genetic relatives.
Because of this, the general rule of thumb is that best results from autosomal DNA tests occur when there is up to about 5 generations back to the shared ancestor. For those hoping to prove relationships beyond third cousins, it may be necessary to test more siblings or first cousins on one side (or both) in order to find a recognisable shared segment of inherited DNA.
Because of this ‘number of generations’ limitation, in autosomal tests it is better to test the oldest living family member (or the one who is in the earliest generation).
What do autosomal DNA test results look like?
The commercial companies’ autosomal tests generally report your matches in the database (and their contact details) with predicted relationships based on the amount of shared autosomal DNA.
Three main companies provide autosomal tests for genetic genealogy. Family Tree DNA calls their autosomal test ‘Family Finder’. 23andMe call their atDNA test ‘Relative Finder’. AncestryDNA also provides autosomal DNA testing.
Currently AncestryDNA does not provide any such chromosome information, directing those who test to look at the public trees of their matches, in the hope that shared ancestors can be recognised. ‘DNA circles’ link people who match DNA and who also have the same ancestor in their family trees.
Family Tree DNA and 23andMe provide ‘chromosome browsing’ tools, showing on which chromosome/s lie any shared segments. Because the test alone cannot distinguish which chromosome was inherited from a mother and which from a father, these chromosome maps appear as images showing only one of each pair of chromosomes. For instance, in the image below the background (dark) chromosomes are mine, and the segments I share with three close relatives are shown overlaying, in different colours.
Simplifying to only showing each pair as a single chromosome means that it might appear as if I match two people in the same area of the same chromosome but maybe I match one on the chromosome inherited from my mother and one on the chromosome inherited from my father. The two predicted genetic relatives may each match me but not each other. I should ask each to check if the other appears in their list of matches.
When a segment is shared between three or more people (meaning at least two besides myself and where each person also matches the others at that same location) then we share the same ancestor – this is called triangulation.
From the websites of all three companies (FamilyTreeDNA, 23andMe and AncestryDNA) one can download the raw autosomal test data in order to upload it to third party sites such as GEDmatch – which provide more tools for chromosome analysis as well as finding matches with those who tested with the other companies.
Admixture predictions are also based on autosomal DNA. Genetic admixture means the interbreeding of mixed population groups represented by our ancestors. This tends to be reported in a summary such as ‘30% British, 20% Northern European, …’. In fact this analysis is based on comparisons against databases which were probably created for other purposes than genealogy and the conclusions may not be accurate.
23andMe call their admixture analysis ‘Ancestry Composition’. Family Tree DNA calls theirs ‘My Origins’. AncestryDNA calls their admixture analysis ‘Genetic Ethnicity’. While these analyses might be interesting, the conclusions are not yet completely reliable.
What to do with the results?
Include in your profile information with the companies the surnames in your ancestry and where those ancestors lived. Contact others likely to be close relatives based on their autosomal testing – starting with those whose surnames or locations you recognise – or where some clue points to the relevant part of your ancestry. You may be able to identify where previously unknown genetic relatives fit into your family tree. Then you can begin to share photographs and information in the same way as with more traditional genealogical methods.
You can also test known second or third cousins in order to identify which portions of DNA you share with them, that must have been inherited from known ancestors, and then see if those same segments are also shared with potential matches identified in the database. This might help identify to which branch of the family a new suggested genetic relative belongs.
By testing the DNA of known relatives, you can also check the family tree you have constructed, to see whether DNA confirms the expected relationships.
Autosomal DNA provides another tool that genealogists can use to find relatives and prove relationships. Its benefit is that it is not restricted to a single line (patrilineal or matrilineal) but instead relates to all branches of our ancestry. Its limitation is that it might not be able to identify relatives with a shared ancestor more than about five or six generations earlier.
Traditional family history research involves looking for documents that name an ancestor – and hoping that everybody told the truth! By contrast, genetic tools that are now available to genealogists tell the truth but do not name ancestors – however they can be used to find relatives and to check the accuracy of our constructed family trees.
Why use DNA testing?
I have an ancestor who was adopted. When I eventually located his original birth certificate, no father was named. I developed a plausible theory about who his father might have been, but I could not find any record to prove or disprove my idea.
In another case my ancestor, John Etherington, a builder, sits at the top of one of my ancestral lines but I cannot find any documentary evidence that he was related to the John Etherington, also a builder, who lived two streets away. Another ancestor, Samuel Etherington, was reputed to also be the Samuel Holmes who fathered another family. To solve puzzles such as these I needed a different set of genealogical tools.
What is DNA testing?
Genetic genealogy testing is all about comparing our DNA with others. Closer relatives share more DNA in common with us than more distant relatives. Genetic genealogy tests examine the areas of DNA where we differ – and predict approximately how closely we are related.
Sometimes we have a particular theory to check and we know in advance the two individuals we wish to compare. At other times genealogists are ‘fishing’ in the DNA ‘nets’, hoping to find unexpected genetic matches who might share an ancestor with us and who might then have information about unknown family branches. In the latter case there are benefits in comparing with as many people as possible. One way to do this is choosing a company with a large database of other people already tested.
DNA testing companies
Currently the main options for genealogists looking for living genetic relatives are the three US companies Family Tree DNA, 23andMe and AncestryDNA (a branch of Ancestry.com).
- Family Tree DNA is the company chosen by most genealogists – and these tend to respond to family history enquiries. Moreover this company’s website has useful tools available for comparing DNA as well as recorded webinars freely available.
- 23andMe offers genetic health predisposition reports as well as ancestry information. Many of their customers chose the company for those health reports and so are less interested in responding to genealogists. A dispute with the US Federal Drugs Administration (FDA) currently prevents 23andMe from providing health reports to new customers except in the United Kingdom and Canada.
- AncestryDNA tests were released first to US consumers and so most of the people in their database are in the United States. Recently AncestryDNA began offering tests to Australians. AncestryDNA test results can be linked to Ancestry trees.
Ordering a test involves going to the company’s website, selecting a test and paying by credit card and then the kit will be posted to you. Family Tree DNA and AncestryDNA tests involve swabbing inside your cheek (with something like a toothbrush) – in the way we have seen on television crime shows. The 23andMe test involves filling a test tube with saliva. In either method customers then post their completed kits back to the company and some weeks later are advised by email when their results are available online. Customers log on to the company’s website with a userID and password to find their results and matching customers predicted to be genetic relatives.
Which test should I take?
DNA testing is advancing (as well as becoming cheaper!) and so is more available for checking theories about your family history and perhaps even breaking down brick walls you might currently face. This article introduces the options currently available that might be useful to family historians.
Test 1: Y-chromosome tests, for males to test DNA inherited from their father’s fathers
For under US$200 we can test whether two males are likely to share a common ancestor ‘within a genealogical timeframe’, and how many generations ago that shared ancestor probably lived.
This test is valid for any two men who might share a male ancestor – they do not need to have the same surname. When testing with a company that has a huge database of people already tested, I might find a match with some living descendant who shares with me a common ancestor. This is useful for all genealogists but perhaps especially for adoptees.
I have used this test to discern whether two families with the same surname were actually related to each other, in the absence of documentary proof. I have also used this test to check (and refute) a theory about who might have been the biological father of an adopted male. It was necessary to find a living male descendant (down an all-male line) from the adopted male and also to find a living male descendant (down an all-male line) from the hypothesised birth father, and then compare the DNA that each inherited from their father’s fathers.
Y-chromosome tests are only available to males, as only males have a Y-chromosome. Females like me need to ask a near male relative to be tested – a brother, father, or uncle. I have ordered tests for my father and also my mother’s brother in order to examine my nearest male lines. For Y-chromosome tests, I recommend using the company FamilyTreeDNA and testing at least 37 markers.
Test 2: Mitochondrial tests, for anyone to test DNA inherited from their mother’s mothers
Useful DNA tests are no longer limited to males. We all have a different type of DNA (called mitochondria) that we inherited from our mother’s mother’s mother. Previously mitochondrial DNA could only tell us about ancient ancestors and their migratory patterns, but now it is possible to obtain much more recent information. Family Tree DNA offers a full sequence test of all our mitochondria, allowing us to identify people who share an ancestor with us on our maternal line within about 100-400 years. That test is also currently available for under US$200.
Test 3: Autosomal tests, to test the DNA inherited half from each of our parents
We are not restricted to testing only the DNA of our father’s fathers or our mother’s mothers. It is also possible to test our remaining DNA, inherited equally from both of our parents – this DNA is called ‘autosomal’. These tests compare the DNA of our ancestors regardless of gender, because we inherit half our autosomal DNA from each of our parents (and via them, from their ancestors). However as we inherit one quarter of our DNA from each of our grandparents (and so one eighth from each of our great grandparents) eventually the inherited material from any particular ancestor becomes so small as to be difficult to identify.
Consequently, when comparing this autosomal DNA with someone else, our best conclusions are when the shared ancestor lived no more than about five generations ago.
Commercial autosomal tests also report on our likely population origins or admixture, for example, ‘60% British, 20% Scandinavian and 20% Jewish’. The sample databases used for comparison are very small and currently most of these predictions are considered unreliable.
Family Tree DNA calls their autosomal test ‘Family Finder’, while 23andMe calls a similar test ‘DNA Relatives’. Both tests cost under US$100 – plus postage. (23andMe’s postage and handling charges to Australia adds another three quarters to the price of their kit!) The AncestryDNA test costs Australians under US$150 (plus postage) but if you do not have an Ancestry.com subscription there is an annual cost for accessing your results.
For any genetic relatives identified in their autosomal tests, Family Tree DNA and 23andMe also report on shared segments of the X-chromosome. Females have two X-chromosomes (inherited one from each parent) while males have one (inherited from their mother). When trying to work out which ancestral branch might have passed down the X-DNA we share with some match in the database, genealogists can look at pedigree charts and eliminate any father-to-son branches, as fathers do not pass any X-chromosomes to their sons.
Use the tests in conjunction
The tests can also be used in conjunction. The autosomal ‘Family Finder’ test through Family Tree DNA identifies matches with my DNA and calculates a likely relationship.
One of my matches (described as a possible 3rd to 5th cousin) seemed to have very similar Y-chromosome (father’s father’s) DNA to my mother’s brother. I made contact and by swapping names of grandparents and their parents we soon identified that he was the son of a 3rd cousin to me (and so indeed within the range of 3rd to 5th cousins).
Autosomal testing can be used to check your constructed family tree.
Comparing the autosomal DNA of the three female cousins (Fay, Ann and Maureen) at the bottom of this diagram confirmed my constructed family tree of their relationships back to their shared ancestors.
(Spouses omitted after the first generation to simplify the diagram.)
It is not necessary to understand how a car works in order to drive it, but it is necessary to know the functions of driving. In the same way it is unnecessary to understand much about the science of DNA – but it is necessary to understand what sorts of questions can be answered by the different DNA tests so you can use them as tools to aid your family history research.
The most recent DNA tests available to genealogists offer useful information which can supplement traditional genealogical methods. Family trees are still needed to identify ancestors and draw conclusions about relationships. DNA tests can supplement this genealogical research, filling in gaps in the paper trails. With such tools we can test our conclusions and assumptions in constructed family trees by confirming or disproving reputed relationships. As more people are tested and databases grow, commercial DNA tests are even more likely to help us find relatives that we might not have found by traditional methods.
DNA technology is advancing so rapidly that it is difficult to keep abreast of the advances and possibilities. Moreover rapidly falling prices make genetic testing more affordable and so more accessible. Here are some current options:
Test 1: Y-chromosome tests, for males to test DNA inherited from their father’s fathers
It is now possible for under US$200 for males to test the DNA they have inherited from their father’s father’s fathers, with sufficient accuracy to determine whether two men likely share a common ancestor ‘within a genealogical timeframe’ and how many generations ago that common ancestor probably lived.
I have used this test to discern whether two families with the same surname were actually related to each other, in situations where I have not yet found documentary proof. I have also used this particular DNA test to check (and finally refute) a theory about who might have been the biological father of an adopted male. It was necessary to find a living male descendant (down an all-male line) from the adopted male and also to find a living male descendant (down an all-male line) from the hypothesised birth father, and then compare the DNA that each inherited from their father’s fathers.
DNA is not related to surnames and so I am not restricted to testing two men with the same surname – the test is valid for any two men who might share a common male ancestor. However when I order this test, if I choose to use a commercial testing company like Family Tree DNA – which has a huge (and growing) database – I might find in their database a match with some living descendant who shares a common ancestor that I did not know about. This is especially useful for adoptees.
The above DNA test is only available to males (as only males have a Y-chromosome). Females like me need to ask a near male relative to be tested. I have asked my father and also my mother’s brother to be tested – this opens up for examination my nearest male lines.
Test 2: Mitochondrial tests, for anyone to test DNA inherited from their mother’s mothers
Useful DNA tests are no longer limited to males. We all have a different type of DNA (called mitochondria) that we inherit from our mother’s mother’s mothers. Mitochondria mutates so slowly that formerly the only conclusions we could draw from our maternal line was about ancient ancestors and their migratory patterns.
However that is no longer true. The company Family Tree DNA offers full sequence tests of all our mitochondria (DNA that is inherited from our mothers) that allow us to identify people who share an ancestor through our mother’s mother’s mothers, within about 200 years. [Thank you Bill Hurst for pointing out that while 23andMe also tests the ‘coding region’ of our mitochondria, they do not test or give results for all 16,571 locations, so theirs is not in fact a full sequence test.]
When the above matrilineal full sequence tests first became available, they cost close to $1,000. That price has dropped now to under US$300 (sometimes under $200).
Test 3: Autosomal tests, to test the DNA inherited half from each of our parents
We are not restricted to testing only the DNA of our father’s fathers or our mother’s mothers. Since 2010 it is possible to test the remaining nuclear DNA (that is, not the sex chromosomes). This DNA is called autosomal. Family Tree DNA calls their autosomal test Family Finder, while 23andMe calls a similar test Relative Finder. (Again these tests are under US$300 and sometimes under $200.)
These particular tests can check the DNA of our ancestors regardless of gender, because we inherit about half our autosomal DNA from each of our parents (and via them, from their ancestors) and this DNA can also be compared with the DNA of others. However as we inherit about one quarter of our DNA from each of our grandparents (and so about one eighth from each of our great grandparents) – eventually the inherited material from one particular ancestor becomes so small as to be difficult to identify definitively. Consequently, when comparing this autosomal DNA with someone else, our best conclusions are when the common ancestor lived no more than about 6 generations ago.
Use the tests in conjunction
While the above tests examine separate DNA, the tests can be used in conjunction. When looking at the summary of DNA results for people that 23andMe identified as likely to be my 3rd to 5th cousins (identified via the Relative Finder – or autosomal test), I noticed that one of the matches also seemed to have very similar Y-chromosome (father’s fathers) DNA to my mother’s brother. I sent an email and by swapping names of grandparents and their parents, we soon identified that this person was the son of a 3rd cousin to me (and so indeed within the range of 3rd to 5th cousins).
It is not necessary to understand how a car works in order to drive it, but it is necessary to know the functions of driving. In the same way it is unnecessary to understand much about the science of DNA in order to use it as a tool – but it is necessary to understand what sorts of questions can be answered by the different DNA tests so you know how to apply them as tools to aid your family history research.
This field is changing quickly
Because genetic tests available to the public are changing frequently (and certainly the prices are) readers need to beware of relying on conclusions written years ago or by someone who has not ‘kept up’ with tests currently available. This blog post is partly in response to an article I read this week entitled ‘The DNA dilemma’ – I do not agree with many of the conclusions in that piece.
It is no longer true to say that the only available information to be derived from maternal DNA (or mitochondria) is about ancient migrations of peoples – recent relatives can now be found by a full sequencing of the mitochondria (test available from Family Tree DNA for under $300).
It is no longer true that autosomal DNA can only make generalised indicators of race origins. (Autosomal DNA is sometimes referred to as ‘nuclear DNA’ but that is incorrect because the sex chromosomes are also inside the cell nucleus and the autosomes are the other pairs of chromosomes that are not the sex chromosomes.) Nor is it necessary to ‘test each generation in turn’. Autosomal DNA can identify that two people shared common ancestors within 6 generations (and possibly beyond, but it is less accurate beyond 6 generations). Many genealogists will not know all of their ancestors back even 6 generations, and so this DNA test can predict likely distant cousins who may not have been found by a paper trail.
There are differences between the DNA tests used in forensic law enforcement compared to commercial tests. Without going into too much scientific detail, legal forensics examine repeating groups of DNA at certain points on the autosomes whereas commercial autosomal tests examine the autosomal SNPs (something like ‘typo’ mutations). The tests are entirely different. Be wary about confusing the markers referred to in tests of the Y-chromosome (the DNA inherited father-to-son) – which are entirely different to the markers of autosomal DNA examined by forensic law enforcement agents.
Some people have suggested that male DNA studies are only relevant between males who share surnames. That is not true. There are many examples where family trees show a son with a different surname to his father – whether the name was changed by deed poll, by adoption, by remarriage of the mother – or for many other reasons. It is not the same surname that defines two people as father and son. Likewise DNA tests do not take surnames into account, so the test result is just as accurate whether two men share a surname or not.
In my opinion, the most recent DNA tests available to genealogists offer precise information which can supplement traditional genealogical methods. Family trees are still needed to identify ancestors and draw conclusions, however DNA tests can supplement other genealogical research, filling in gaps left by paper trails. With such tools we can test our conclusions and assumptions in constructed family trees as DNA can confirm or disprove reputed relationships. As databases grow, commercial DNA tests are more likely to help us find relatives that we might not have found by ‘traditional methods’.
I started down the DNA learning path several years ago. My Dad’s father was adopted, & when I eventually found his birth certificate it contained no information about his father. An unusual middle name and circumstantial evidence suggested someone, but with no documentary evidence, DNA seemed a way to test my theory.
I found a grandson of this possible ancestor – son of a son, so a good candidate for y-chromosome DNA comparison with my father. I asked – if I paid for it, would he be willing to have his DNA tested to compare with my father’s DNA? He said yes, but unfortunately the test proved that he and my father were not related. (DNA is often better at disproving rather than proving relationships.)
I used the company Family Tree DNA, which has the largest database for testing and comparison, and now that I am registered, I am advised when others match my Dad’s DNA. I hope that one day I will find someone with the right DNA,who had an ancestor in the right place and at the right time.
Some time later, I had the opportunity to speak to Megan Smolenyak about my problem & confirm my method. I asked Megan for her advice about which company should I use to test my Mum’s DNA.
Females don’t have y-chromosomes so cannot have the y-DNA tests done. However humans have other DNA outside the cell nucleus, called mitochondrial DNA (mtDNA). Mothers pass mtDNA to all their children, but only their daughters pass it on. I wanted my Mum’s DNA to be tested now and also stored for the future, for as-yet-undeveloped tests. Forensic scientists use mitochondrial DNA now, but for genealogists mtDNA is mostly only used for deep ancestry testing, not for finding ‘recent’ ancestors (those in a genealogical timeframe).
Megan suggested that I have my mother’s DNA tested with the company 23andMe, as they were developing new tests and could offer more information about female ancestors. 23andMe tests give information about genetic health issues, in addition to genealogical ancestry matching – so I took that advice.
These 2 companies that I had used (23andMe & FamilyTreeDNA) offer very different information in their test results. Results from the FamilyTreeDNA tests are tables of numbers, indicating the DNA at specific genetic marker points. There is also a YSearch database for comparing results, and even people who have had their DNA tested with other companies can search this freely – you manually enter the numbers (alleles) at various marker locations and see if the results match anyone in the YSearch database.
The results from 23andMe gave information about genetic health risks and tendencies and general DNA groupings – it required a bit more delving to actually find the numbers that correspond to the (mitochondrial) DNA markers.
Around a year ago, both these companies announced new tests involving autosomal DNA. 23andMe call this ‘Relative Finder’ – FamilyTreeDNA call it ‘Family Finder’. Humans have 23 pairs of chromosomes in every cell nucleus – 22 pairs of autosomes and also another pair, the ‘sex chromosomes’ (XX for females, XY for males). The autosomes contain bits of DNA inherited from all your ancestors, not just from all-male or all-female lines. You share larger pieces of DNA in common with close relatives, and smaller bits of autosomal DNA with relatives less closely related.
Both males and females have this autosomal DNA, so now you can find relationships with anyone sharing any common ancestor, not just the all-paternal or all-maternal lines. This new autosomal DNA test has thrown up some new possibilities and new candidates in the search for my father’s father’s heritage. (We already have found a close relative with interesting possibilities.)
However, back to the initial subject. The company 23andMe is offering a special price for the next few days, and some Facebook friends decided to take advantage of it. I agonised whether I should join them, given that I already have tested my father’s DNA as well as my mother’s mitochondrial DNA.
In terms of autosomal DNA, although the test is new, I suspect that the company FamilyTreeDNA is likely to have a bigger database for comparisons. (For me the main value of DNA tests is looking to match with others, and so larger databases are better.)
But 23andMe gives other information – about genetic related diseases – in addition to the study of ancestry. I have decided that both companies’ tests are of interest to me. So now I too have taken advantage of the current special price, and will get my own DNA tested.
Of course there are many other testing companies, and websites with information about DNA. I give talks about ‘DNA for Genealogists’ (my handout can be found on my website). The handout contains information about various testing companies and their information pages, as well as other sites with DNA tutorials, mailing lists and even a DNA Wiki.
For now though, I have joined the ranks of those waiting for a test tube to be posted to me, so I can take the next step in this DNA journey.