FAQ
Life can be complicated and so can DNA which should not be too surprising given DNA is the building block for life itself! In life there are no absolutes, no simple black and white answers for every situation. The same for Y-DNA.
However, life situations can be made simpler if an overview is taken that looks at the essentials and by-passes confusing detail. Everyone at first has problems understanding their Y-DNA test results, however no-one needs to be a scientist to understand Y-DNA. Also more often than not, the results are quite different to what people expected or thought they would get. As this scenario plays out time and time again with new testers, this simplified overview of Y-DNA is intended as a starting place to dispel misconceptions and provide some understanding of what Y-DNA can and cannot do.
Testing companies market Y-DNA on ‘potential’ results but ‘actual’results rarely match the ‘full potential’ expected. Although this can be disappointing, it does not lessen the potential of the test.
Y-DNA is essentially about matching and therefore a 'team activity'.Without group participation there can be no results to compare and match. A Catch-22 situation as without all the people that have already tested no matching could be done. For those who find they have no matches, someone has to be the first but the potential to find new matches with time is the same for everyone as more people test.
Jargon that needs to be understood (but not scientifically) as it is mentioned often is:
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haplotype |
Technical term for men who have Y-DNA tested. |
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haplogroup |
Major groups or branches on the Y-Tree represented by SNPs likeR1bM343->M269->L21->M222 etc. These in turn are divided into smaller groups or ‘clades’ which divide again into ‘subclades’ The diagram athttp://www.familytreedna.com/groups/r-1b/about gives a general illustration. |
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STRs |
The 111 marker values/counts that go up and down, back and forth,round and round that are also referred to as alleles. A ‘close’ STR match with a Genetic Distance GD between 0 and 2 for 67 markers may indicate a potentially close relative. |
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GD |
Genetic Distance should not be confused with generations. GD is the number of STR markers that do not match when comparing two men. The number of markers being compared is also important as a GD of 1 at 37 STRs is a significantly different/more distant than a relationship with a GD of 1 at 111 STRs. For how to interpret GD see http://www.familytreedna.com/learn/y-dna-testing/y-str/two-men-share-surname-genetic-distance-67-y-chromosome-str-markers-interpreted/ |
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Phantom Ancestor |
Dueto the random nature STR changes it often causes the STR values of unrelated men in different haplogroups/subclades to converge and suggest a relationship due to aclose GD. To eliminate Phantom Ancestors the rule is, only compare STR values with men in the same haplogroup/subclade. Obviously the younger the subclade the less men to compare but the more meaningful the relationship. |
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SNPs |
One-off mutations that are irreversible (unlike STRs) that are passed unchanged from father to son. For more about STRs and SNPs see http://www.familytreedna.com/groups/r-1b/about/background |
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NV |
Novel Variants (or singletons) are the ‘unmatched’ SNP mutations. SNP mutations that are unique to just one man awaiting another man to test and match are Unique Novel Variants (UNV). However, once matched, the variant is no longer ’unique’ or ‘novel’ so becomes officially a SNP. |
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Terminal SNP |
The term 'terminal' is misleading because all it represents is the youngest currently 'known' SNP to be in common with another person. After the 'terminal' SNP are all the 'unknown' Novel Variants unique to one person and no-one else. That is until another person NGS tests and finds they have the same 'Novel Variant' mutation in common which then becomes the youngest' terminal' SNP for those two men which also adds a new branch/twig to the Y-Tree ... and so it goes on until eventually one matches up all their Novel Variants ... maybe then one could truly say their 'terminal' SNP has been found. |
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NGS |
Next Generation Sequencing is a SNP ‘discovery’ test that firstbecame affordable in 2014. FTDNA’s Big-Y and FGC’s Full Genome 2.0 are the only two NGS tests available. NGS tests 76% of the Y-chromosome to find/discover known and unknown SNP mutations.Once the test has been analysed and comparisons made (usually by a third party ie not always the testing company) the lowest/youngestmatch on the Y-Tree will be known together with the age range forthe SNP together with Novel Variants for future matching. |
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Y-Tree |
Atree like arrangement of SNPs with the oldest (most common) at the top descending and branching to the youngest (most recent) SNPs at the bottom. |
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Derived |
Means tested +ve, or in other words the man or haplotype ‘has it’ |
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Ancestral |
Means tested -ve , or in other words the man or haplotype ‘does have it’ |
With Y-DNA it is possible to trace aman’s paternal line from 20,000 years ago to present. Currently inorder to maximize the potential discoveries that Y-DNA can uncover, a Y-67 or Y-111 STR test combined with a NGS test like Big-Y is needed. However part discoveries can be made with STR testing alone. Further testing with SNP Packs has the potential to find the youngest known SNP but currently this is unlikely to be within a genealogical time frame. Below is a table summarising what each Y-DNA test can and cannot do:
|
Test |
Cost (US$) |
Can |
Chance Correct |
Cannot |
|
Y-37 STR |
$169 |
|
80-100% 0-70%
70-80% 20-60% |
|
|
Y-67 STR |
$268 |
|
90-100% 0-80%
80-90% 0-50% 50-70% |
|
|
Y-111 STR |
$359 |
|
95-100% 80-100%
90-100% 0-80% 60-80% |
|
|
SNP Packs |
$119 |
|
80-100% 90-100%
95-100% 99-100% |
|
|
Big-Y |
$575 |
|
95-100% 95-100% 95-100%
95-100% 95-100%
99-100%
99-100% |
|
For more information about SNP testing go tohttps://dna-explained.com/2012/08/10/to-snp-or-not-to-snp/ (note this 2012 information was before NGS testing became available/affordable in 2014).
The essentials of Y-DNA are:
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STR test to :
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Conservatively estimate a haplogroup;
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Find for surname matches with a close GD.
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-
SNP test to:
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Better define the relationship with surname matches;
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Find men with different surnames but who match the same SNP.
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-
NGS SNP ‘discovery’ test to:
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Discover Novel Variants;
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Match Novel Variants with other men and grow the Y-Tree;
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Find relationships within a genealogical time frame by eventually finding matches for all Novel Variants.
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-
Many people testing, the more the better and the wider the coverage/countries the better. If a NGS test like Big-Y is an option there is no need to SNP Pack test like the R-M343 Backbone.
In 2006, at the start of the FTDNA R1b ALL Subclades Project it had 100 participants, now 10 years later has grown a hundred-fold to over 11,000.
The field of DNA genetic genealogy is very new and it has been citizen scientists at the forefront of discoveries in the past 10 years. The citizen scientists making progress in Y-DNA include the volunteer project administrators who provide advice and help with no financial assistance from any testing companies or outside organisations. So what is currently known is largely due to project administrators/citizen scientists and the collective pool of DNA data from the 10,000s of people who have already STR tested and the 10-15% of men who have gone on to take a NGS test.
Trust the table summarising what Y-DNA can and cannot do helps people new to Y-DNA with their decisions on what test(s) to take.
Written by Alan Kane, NZ
What is the DONATE button?
The Donate button is where project members can voluntarily donate funds to the group fund which can be used for various purposes such as sponsorship of tests for other members. Donations to the Ireland yDNA project can help to pay for SNP testing which helps us learn more about the branches of the y-haplotree which occur in Irish yDNA.
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All, as many of you know the "Colorized Chart" under the DNA Results tab will throw an error (Houston we have a problem), this issue has been raised a number of times and has let to be fixed by FTDNA. While doing some experiments this morning I think I found a work around that will fix it for most people. You need to do following:
1. In the "Markers" drop down select the level of testing you've done (eg. Y-DNA67)
2. Untick the "Show all columns" tickbox
3. Change the page size to 9,000, you should than be able to view report and do a "ctrl-F" (find in page) to find your specific kit number.
Regards
Paul Duffy
updated June 2019 (Margaret Jordan)