(And how we use it in Taylor Family Genes)
Y-DNA has become a powerful genealogical tool to identify male ancestors in common with others. It is a valuable supplement to traditional documentary genealogy; it is not a substitute for it.
Read this excellent DNA 101 by John Blair for an in-depth discussion of the science. Also, Dr. Bruce Walsh's explanation of the math.
All males -- and only males -- have a Y chromosome; the dioxy-ribonucleic acid (DNA) in the Y chromosome is called Y-DNA. It is passed down, from fathers to their sons, almost always without change for many generations.
Comparing the Y-DNA of two males can say whether they share a common male ancestor, abbreviated CMA, and yield a probability estimate for the number of generations to the CMA. Comparing the Y-DNA of one man to a database of samples collected from throughout the world can shed some light on the ethnic & geographic origins of very distant paternal ancestors.
However, Y-DNA follows only the direct & unbroken paternal line. It says nothing about female ancestors. Imagine a pedigree chart, where fathers are represented above mothers: Y-DNA traces the top line of the chart.
The testing process is user-friendly. Swab the inside of your cheek with a brush-like device or Q-tip provided by the testing company to get a sample; this collects skin cells from inside your mouth. Place the swab brush in the sterile container provided and mail it back to the testing company's laboratory in the mailing container also provided.
In a few weeks, the laboratory will have done its highly-technical thing, analyzed the Y-DNA & notified you of the results.
Women do not have a Y-chromosome, but they have fathers, brothers and uncles who do. They can purchase a kit and collect a sample from one of the men, then submit it under their name. When DNA submitted is not the "kit owner's", it will represent the sample donor, not necessarily the owner.
Members & prospective members often ask us how many markers members should order tested. Cost is a consideration, because the panels with more STR markers cost more than the minimum 12-marker panel.
We recommend that -- due to the commonness of the Taylor surname -- 37 Y-DNA markers is the minimum to order. For us Taylors, the lowest-cost 12-marker panel is false economy because an upgrade (at more cost) will usually be needed to "rule in" a common paternal ancestor. A perfect 12/12 match contains insufficient information for reliable interpretation.
If your only interest is to "rule out" a relationship, a 12-marker test may be sufficient. Disagreement on two or more of the markers indicates the test subjects do not share a paternal ancestor within genealogic time.
The 12-marker test will elicit many "false positives" -- others who match on the 12 tested, but would not match if more markers could be compared. We recommend against the 12-marker test for the Taylor surname.
The 37 marker test includes a balanced panel of thirty-seven Y-chromosome Short Tandem Repeat (STR) markers. This is the minimum test we recommend to trace the paternal ancestry of males for genealogy purposes. The additional markers from 26-37 refine the predicted time period in which two individuals are related and eliminate unrelated matches. A perfect match at thirty-seven markers (37/37) indicates the two individuals share common ancestry in recent times.
The 67-marker further refines the time/probability window as to the most recent common ancestor. The interpretation is even better for a match of 67 out of 67 markers! A newly-available 111 marker test can be helpful in two ways:
However, the FTDNA TiP tool may be even more helpful -- even at 37 markers -- in choosing which of your matches deserve priority. (The TiP icon shows beside the name of each match.) Use TiP to calculate the cumulative probabilities at each generation for the most recent common ancestor. Record the generations numbers where the probability reaches 90% (or some other percent). Those with the lowest generation numbers are more recently related to you. Or, record the 8-generation probability; those with the highest numbers are more likely related.
FTDNA -- more than other genetic genealogy providers -- sponsors surname, geographical and other types of projects for customers' benefit. These projects have advantages for members who join them, including:
Our project (Taylor Family Genes) is for the Taylor surname and variations of it. The project provides an unusually wide range of services to its members.
You'll receive a certificate of the results and a and report describing the testing process. For STR testing (the most commonly used), the certificate will have a list of Y-chromosome marker names and each marker's corresponding allele value.
"Marker" (see the glossary) is a term with different meanings in DNA. Here, we use it to mean a place or locus on the Y-Chromosome.
How long that list of markers & values is depends on the level of test you paid for. We recommend at least 37 markers for reasons above.
But, the results mean nothing in isolation from others' results; they must be compared to something to draw any conclusions. We call that process of comparison and drawing conclusions "interpretation".
The goal of Y-DNA testing is to find a match which indicates a common ancestor within the genealogical time frame, i.e., less than 800 years ago.
A "match" exists when two (or more) men's Y-DNA agree sufficiently on the STR allele counts for the markers tested in common to suggest that they share a common paternal ancestor. The quality of matches is described by any of these methods:
In general, the more markers that agree and the lower the genetic distance, the more likely it is that two men share a common paternal ancestor and the more likely that this ancestor is more recent.
OK, genetic distance (abbreviated "GD") is a little complicated to explain. Start with the concept that most markers are thought to mutate only one allele (step) at a time. So for most markers, genetic distance is simply the sum of the absolute differences between the markers compared. Except: Some markers are capable of changing more than one step at a time; for these markers, any difference contributes a genetic distance of one (1).
| Genetic Distance Illustration | |||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Name | DYS 393 |
DYS 390 |
DYS 19 |
DYS 391 |
DYS 385a |
DYS 385b |
DYS 426 |
DYS 388 |
DYS 439 |
DYS 389i |
DYS 392 |
DYS 389ii |
Σ GD |
| Al | 13 | 22 | 14 | 10 | 12 | 14 | 11 | 14 | 11 | 12 | 11 | 27 | - |
| Bob | 13 | 22 | 14 | 10 | 12 | 14 | 11 | 14 | 10 | 12 | 11 | 29 | |
| Genetic Distance |
0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 1 | 0 | 0 | 2 | 3 |
Note that, in this simplified illustration, Al and Bob match on 10 of the 12 markers; they have a difference of 1 at one markers and a difference of 2 on another. The total genetic distance between them is 3, for a 3:12 match.
Two types of matches are of interest to us:
FTDNA selects only certain matches to report, based on the number of markers compared and the total genetic distance; it will not report matches for which genetic distance exceeds its thresholds. The FTDNA reporting thresholds are:
In our experience, these reporting thresholds are typically generous. They report matches well beyond genealogical significance. There are, however, certain (rare) types of mutation events which can produce genetic distances large enough to throw the system off-kilter.Check with a member of the admin team if you think one of these applies to you.
We believe that knowing you may share an ancestor with another person is not much value if that ancestor can not be identified by name, dates, places and other characteristics -- all the stuff that's expected of genealogy. Therefore, we distinguish the best quality of reported matches as genealogically significant.
An exact match, where all markers agree and genetic distance is zero, is a special case of a significant match. Exact matches across 12 markers are not considered significant, but may be significant for 25 markers and is significant for 37 or or more.
The overall criterion for declaring a genealogically significant match within Taylor Family Genes is this:
Y-DNA indicates a high probability of sharing a common male ancestor who lived since 1350 AD*.
This plain-English statement relates the DNA evidence to genealogy and is then translated into quantitative criteria, based on the number of markers compared and the number which agree (or the genetic distance):
Please note that these criteria are more restrictive than those used by FTDNA to report matches within its total database, nor are they dependent on surnames matching. Also note that they are more restrictive than past project criteria; some older groups were formed under looser criteria but have not been "revoked". We encourage those with 12- and 25-marker matches to upgrade their testing levels in order to benefit from the higher precision of the 37-marker and 67-marker tests.
* The year 1350 AD represents the usual earliest beginning of the Genealogic Time Frame in England, a time period for which it is possible to identify ancestors by name, date, place and other characteristics. For specific families, the genealogic time frame may extend further into the past. For others, it may be more recent.
When another person shows identical or close results within the FTDNA database and if both parties have signed the Family Tree DNA Release, then FTDNA will inform both members of the match. If the match is for 25 or more markers, your e-mail message will look something like this:
From: info@familytreedna.com
Sent: Tuesday, April 13, 2010 5:53 PM
To: member@domain..net
Subject: Family Tree DNA Kit# 999999 Y-DNA25 Test MatchA 25 marker match has been found between you and another person in the Family Tree DNA database!
You and the other person(s) have matched in 23, 24 or 25 loci. If you share the same surname or variant, this means that there is a 99% likelihood that you share a common ancestor in a genealogical time frame. If you match another person without the same surname or variant, you still probably share a common ancestor, but this ancestor may have lived in the time before surnames were adopted.
The link below will take you to your Family Tree DNA Login. From there you can see a list of your matches. Newer matches will be at the top of the list. Additional emails will be sent to you as we find new matches between you and your "genetic cousins."
Follow the link below and type in your Kit Number and Password to access your personal page
http://www.familytreedna.com/Login.aspxYour Kit Number is 999999
Your Password is X9999If you have not done so, please remember to add your results to Ysearch.org, the FTDNA-sponsored public database. Click on the Y-DNA Matches tab to see an explanation and a link for the upload.
Family Tree DNA
http://www.FamilyTreeDNA.com
info@familytreedna.com
The world's first and largest Genetic Genealogy organization--------------------------------------------------------------------------------
This message was processed by the FTDNA Email System.
The original headers are:
To: member@domain..net
CC:
GUID: a6a405c5-48de-4845-8026-14c4fa27143e @ 5.182
If you are a Taylor Family Genes member, the TFG administrator will get a notice looking like this:
From: info@familytreedna.com
Sent: Thursday, April 08, 2010 7:01 PM
To: admin@domain.net
Subject: Taylor Project Member has a Family Tree DNA Y-DNA25 MatchA Y-DNA25 match has been found between Kit 999999, Firstname Middlename Surname, a member of your FTDNA Group Taylor, and another person(s) in the Family Tree DNA database. He and the other person(s) have matched in 23, 24 or 25 loci, which means there is a 99% likelihood they share a common ancestor.
Please direct your member to the link "Understanding your results" at your personal page, where he will find an explanation about the significance of matches. Also, please remind him to add his results to www.Ysearch.org, the FTDNA sponsored public database. When going to the Y-DNA Matches tab and he will see an explanation and a link for the upload.
Follow the link below to access your Family Tree DNA Group Administrator's page.
Your Kit Number is {Admin #}
http://www.familytreedna.com/login.aspxhttp://www.FamilyTreeDNA.com
"History Unearthed Daily"--------------------------------------------------------------------------------
This message was processed by the FTDNA Email System.
The original headers are:
To: admin@domain.net
CC:
GUID: b59970e3-e818-4556-be60-59f64af6616e @ 5.182
You may notice that neither message identifies the party to whom you match. For that information, you need to log into your personal page at Family Tree DNA. Input your kit # and password (both in your message) and when you reach "My FTDNA", click any of the "Y-DNA Matches" links. The website will generate a list of matches according to the specifications you've set. (You may have chosen not to see 12-marker matches or matches outside the Taylor surname. We recommend the first, but not the second.)
The project administration team may send you a follow-up to the FTDNA notice. It will describe the match and its genealogical significance. It may recommend action you can take to improve the meaning.
Yes. You should post your results to a free, open & searchable Y-DNA database such as Ysearch and Ybase. Ysearch, with 70,000 haplotypes in its database, is sponsored by FTDNA, but accepts results from all testing companies. Ybase, with 15,300 haplotypes, is sponsored by DNA Heritage and also accepts all results..
We've published a Ysearch page on this site to help people upload to it and use it.
Your match may or may not be a member of the project. If two or more project members have a significant match, we'll assign them to a "matched group", for a common paternal ancestor. There is more about this on our Groups page.
If your match is with a person who is not a project member, we can not assign them (or you) to a Taylor matched group. Most project members have at least some matches with person outside the project.
About 8% of our project's members have no matches reported The answer is yes to "rare DNA" much less often than the question comes up. Before coming to that conclusion:
Most often, it turns out that it isn't one marker with one big difference from the most frequent value. It's several markers with small differences.
Interpreting the specific meaning of a match can become complex because `it relies on probabilities. While probabilities are widely used in science, many people are uncomfortable with probabilistic statements. We need them because DNA mutations are random events and can not be predicted in absolute terms.
The purpose of Y-DNA match interpretation is to decide whether a found match is worth pursuing. Does it warrant the hard, slogging documentary research needed to identify the CMA by name, dates, places and other specifics?
We usually do not know the Y-DNA of the common male ancestor (CMA) in a match. We only know the similarities and differences between samples of two living Y-DNA donors. As we work back through the diverging lines to the CMA, we need to consider the possibility of mutations in either or both lines.
A transmission event (TE) occurs when a parent passes DNA to a child and the DNA has the opportunity to change. Transmission events are the spaces between generations and we need to account for the TE in both lines. Within the same time window there will be two sets of TE, one for each line.
The diagram depicts the transmission events in two lines diverging from a
CMA. The total number of TE in this example are 12 (7+5). The two donors are
separated by 12 TE.
Think of transmission events as all the generations in one donor's line from the CMA plus all the generations in the other donor's line from the same CMA minus the two donors' generation. It's similar to the "degrees of separation" game.
Probability has no "sure things"; words like chance & odds permeate throughout. The type of probabilities we look for are are "cumulative"; they represent the chances of sharing a CMA within a specified number of transmission events. Here are typical graphs for 37 & 67 markers. Click the graphs to see larger versions.
 |
 |
| For a 37/37 (0:37) match, chances of the donors being separated by no more than10 TE are ~80%. | For a 67/67 (0:67) match, chances of the donors being separated by no more than 10 TE are ~90%. |
Different people relate to information in different ways. Some absorb it one way; others another way. Therefore, we present different approaches, all based on the same underlying principles that similarity of haplotypes indicate a common ancestor and the degree of similarity the number of generations separating the two sample donors :
We should be cautious about the implied precision of the statistics for these reasons.
Despite these cautions, we believe the calculations are adequate to answer our underlying question: "Is this match worth investing my time and effort?"
When matches exist in a group of three or -- preferably -- more it may be possible to estimate the CMA's haplotype and use differences from that estimated haplotype to determine specific branches with that family's tree. This is a refinement on match interpretation which can only be employed for matching groups of sufficient size.
Triangulation is a complex subject and it's discussed more thoroughly on our "Triangulation" page here.
When a high-quality match is found, your fun has just begun. You will want to contact the other party (& he or she to contact you) to share information toward the goal of identifying the common male ancestor. Perhaps, you both descend from different sons of the same father.
You will want to ensure that your contact information is available to the person with whom you match, so keep it current. In these days, e-mail addresses are especially important. Most people will use e-mail primarily.
Along with the DYS markers & allele values, FTDNA will report the predicted haplogroup into which your DNA falls; if it is unable to predict, its SNP Assurance Program will conduct additional testing to definitively establish the haplogroup. You may also order analysis to specifically identify the haplogroup and its subclade.
A haplogroup identifies broad groups of different strains of Y-DNA -- main branches on the human family tree. Because haplogroups are associated with particular places, this tells you something (e.g., ethnicity & geographical origin) about your distant paternal forebears who are otherwise lost in the mists of time before recorded history. A haplogroup determination speaks to deep ancestry; it is less useful within genealogic time.
A haplogroup designation starts with a capital letter, which may be followed by alternating numbers and letters, e.g., "R1b1b2a4". Each number and letter further refine the designation, but do not change those which precede it. R1b1 and R1b2 both belong to the broader group, R1b.
Haplogroups are further discussed here.
Due to technical difficulties and amount of content, we've moved this section to a separate page. If the definitions in the list do not display, click here.
Our project members have had genetic genealogy success stories to share. Here are a few with the names deleted.