Frequently Asked Questions about yourDNA.family,
it's terminology and best practices:
I have tested for Y-DNA. Should I test for atDNA as well?
You will get a lot of added benefit from testing for autosomal (atDNA) DNA as well. Where Y-DNA gives you information on your all male line only, atDNA will give you hints on all your ancestral lines. Some overlap is there but eg for your Great-Grandfather Y-DNA would just explain 1 out of 8 lines. AtDNA explains all 8 lines on the other hand.
I've done an atDNA test with company x. Now what?
We assume you're interested in the ancestry side, not the health side. Going through thousands of matches is tedious though as a general strategy you should always order them by the amount of DNA you share. Hence we've build this app so we can guide you in the process. Next steps are sorting out who is a real match in recent times, grouping them together by chromosome and where the shared segment is. Map them on either you paternal or maternal side or even further up the family tree. Work with them on comparing family trees, possible location overlaps. Identify (most recent) common ancestors.
What is triangulation?
Triangulation means formation of triangles. In DNA genealogy we would analyze if A (you) would match both B and C (your matches) at the same location & chromosome AND that B would also match C at the same location. Example:
A matches B at chr 1 from 83,561,856 - 154,688,278
A matches C at chr 1 from 83,752,670 - 154,691,672
B matches C at chr 1 from 88,470,251 - 116,916,652
All 3 of them form a triangulated group at chr 1 from 88,470,251 - 116,916,652 as this is the area where they all overlap.
Isn't the in-common-with report at FTDNA triangulation?
No, unfortunately it's not. The in-common-with (ICW) report says only that A (you), B and C (your matches) all match each other. It doesn't tell you however if B and C match at the EXACT same location & chromosome as you match both B and C. It can be the case but in many cases it will not. It can be that B is matching you on your paternal side and C is matching you on your maternal side. Yet B and C match each other on a non-related line to you.
Can I find my biological parents with your app?
Finding biological parents requires following every possible lead on every possible service where people have DNA (uploaded or tested).
We're connecting you to these services and automate every possible step so you can concentrate on communicating with your closest (new) relatives to improve your chances of finding your biological parents eventually.
I have no information beyond my grandparents. Can I still use your app?
Though a well filled family tree is better, we will help you in filling those gaps. We will confirm who is sharing an ancestor with you, arrange them into groups and you will work together with them on combining the information in their trees to see where you connect.
Where should I buy my DNA test?
All (three major) companies have their pros and cons, especially when it comes to what tools they offer to identify which is a "good" or a "bad" match.
To us it doesn't matter as we want to deliver the best possible tools to help you (and our own family research). 23andMe, Family Tree DNA and Ancestry all provide autosomal DNA tests where you can download your results. That's all that is needed to start.
Aren't all matches presented by the testing companies "good" ones?
Identifying if a match is indeed related to you in recent times requires a lot of complicated and time consuming steps, amongst them phasing and triangulation. Our app does these steps automatically for you, so that you can concentrate to collaborate only with your ("good") DNA cousins. So some of them are wrong, research by some genealogists have revealed over 30% of them are indeed "bad".
What is a MRCA?
MRCA stands for "Most Recent Common Ancestor". Once you've identified through triangulation that you and 2 other previously unknown people all descend from one common ancestor (CA), it's highly likely that you have a shorter path to one of them .
So if match B is actually a 2nd cousin, it means you're related through your Great-Grandparents which is the MRCA. Now C might be a 3rd or even 4th cousin, meaning your MRCA with him/her will be at the 2G-Grandparents or 3G-Grandparents level.
I thought the CA is a single person?
Yes and No.
The common ancestor (CA) in a triangulated group (TG) is the person where all family trees of all DNA cousins in the TG would go down from. As we can't tell with the current DNA sequencing technology if that segment came from the Father or Mother, the CA is a couple. If we later find a match further up the tree, the CA becomes a single person (MRCA) but the new CA still will be a couple.
Fellow research colleague Paul Rakow pointed to an exception of this rule. His CA points to a female ancestor who was married twice. As the other DNA cousins are descendants of the female ancestor through a different husband it's clear that in this rare case the CA is a single person.
What is the required length for a X-DNA segment?
The X chromosome is much different than the 22 autosomes. Recombination is even more irregular than on the autosomes. What is most important when you look for a generally accepted minimum length is the gender between the two people that you want to compare .
For two males you can go down to 1cM (centiMorgan) and 200 SNP's (single- nucleotide polymorphism).
For comparing a male with a female you can use 6cM and 600 SNP's.
For comparing two females or a person who's gender is unknown you use again 6cM and 1200 SNP's.
No X-DNA shared with a match. Is this match on the paternal side?
X-DNA follows different rules than the autosomes who are given to each child by both parents. Whilst a mother gives her X-chromosome to both her daughter and her son, a father isn't giving his X-chromosome to his son, he gives it only to his daughter who needs to X-chromosome.
Now while it's possible that a missing X-DNA segment indicates a paternal relationship, in many cases it's just that the X-DNA inherited by both was lost on one or both sides. So the absence isn't a clear indication of a paternal side match. But the reverse is true, a son must have got his matching X-DNA segment from his mother!
Why does FTDNA and GEDmatch show different matching segments for the same people?
Each DTC (direct-to-consumer) DNA testing company and 3rd party services like GEDmatch (or our own service) has a different algorithm (basically rules). There is no ultimate algorithm that is the best. They have different distributions of populations (some have more international customer, others more US focused) and each has it's own approach as to how many wrong (meaning IBC/IBS) matches they show you.
See the question:
Aren't all matches presented by the testing companies "good" ones?
What are false positive or IBC/IBS segments?
IBC (identical by chance) refers to segments that we're "stitched" together and are random. IBS (identical by state) refers to segments that are given down to a large number of people (eg a genetic modification) and like IBC aren't helpful in identifying a common ancestor.
False positive is used in Statistics to describe a "false alarm". It shows in our case that someone is matching us when indeed he/she isn't. Triangulation identifies them as IBC/IBS.
Suggested further reading:
When is a DNA segment match a real match? IBD or IBS or IBC?
Does FTDNA offer the same amount of raw data as 23andMe?
No, each DNA testing company is testing different markers (SNP’s) on their custom chip and this is subject to change every couple years as the technology becomes better and cheaper (23andMe for example is on version 4 of their testing chip). Right now 23andMe is testing 577,382 SNP’s vs FTDNA with around 690,000. So yes you get more markers however more isn't always better.
I'm writing this as 23andMe is offering more in their test, that you would need to pay for with an additional test at FTDNA. You get both a mitochondrial (mtDNA) and Y-DNA haplogroup prediction for free with 23andMe (currently no other DTC offers this).
Is the mtDNA / Y-DNA test at FTDNA the same as what I get for free at 23andMe?
No. The only thing in common is that you get a prediction of your paternal (Y-DNA) or maternal (mtDNA) haplogroup.
FTDNA offers Y-DNA / mtDNA tests that give you way more detailed information. E.g. 23andMe tests 19% (2737) of the totally available markers on mtDNA whereas FTDNA offers the whole mtDNA genome!
The same is true for Y-DNA, FTDNA offers tests with a different technique (Short Tandem Repeat = STR) but also tests a big amount of Y-DNA SNP's, hence their product name Big-Y. The Big-Y puts your haplogroup way further down in the phylotree (the tree of mankind) and you can help expand this tree.
What is the best/most affordable medical DNA test?
It's currently the Family Finder test from FamilyTreeDNA for 79 USD plus postage if you live outside of the US (can be costly). If you can wait, they have promotions like e.g. for Xmas where they lowered the price down to 59 USD.
Please note that you need to download your raw DNA data and upload it to Promethease (current price 5 USD) as FTDNA doesn't offer any medical DNA test.
Otherwise 23andMe offers a medical DNA test for currently 199 USD plus postage.
Please do note that 23andMe offers the most medical markers in their raw DNA data, as FTDNA primary concentrates on ancestral markers (but some health related is included).
I'm adopted. Which DNA test is the best to find my ethnicity?
Any autosomal DNA test is best because it analyzes your DNA along all ancestor lines. A Y-DNA or mtDNA test would only tell you the ethnicity of your all male/ all female line. For those with Chinese ethnic background I suggest to also try WeGene (wegene.com) as it naturally has a lot of Chinese testing for it
As for the medical aspect I refer to my answer here: What is the best/most affordable medical DNA test if you are uninterested in ancestry?
What is the best DNA ancestry test one can purchase?
Different people reported different experiences as they value certain criteria higher than others. A couple of points to consider:
- The number of relatives you get
- Quality of family trees and paper trail research
- Quality of reports and tools provided
- Responsiveness of your matches to requests
- overall size of their database of atDNA tests
- ease of use of their website (user experience)
If you have the money, try all three big DNA testing companies and upload your data to 3rd party websites that allow comparisons across DNA testing companies.
My more detailed answer is here: What is the best DNA ancestry test one can purchase on the internet?
Which offers better ancestry composition estimates between FTDNA, 23andMe and AncestryDNA?
In my opinion 23andMe offers the best ancestry composition reports. These are the factors that were important for my decision:
My more detailed answer with screenshots from all three DTC is here: Which offers better ancestry composition estimates between FamilyTreeDNA and 23andMe and why?