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Y-DNA Match Interpretation

From http://www.familytreedna.com/faq/answers.aspx?id=9#919 on 11 July 2013


What is the expected relationship with my match?

faq id: 919

The expected relationship between you and your Y-chromosome DNA (Y-DNA) match is dependent on both the number of markers you have tested and the genetic distance. The chart below shows the interpretation of your relationship at each testing level (Y-DNA12, Y-DNA37, etc.) for relevant genetic distances.

For example, if you and your match have both tested at the Y-DNA37 level and are a 36/37 match this is a genetic distance of one. You are then considered tightly related.

Relatedness Genetic Distance Steps for Y-DNA Interpretation
12 25 37  67  111
Very Tightly Related N/A N/A 0 0 0 Your exact match means your relatedness is extremely close. Few people achieve this close level of a match. All confidence levels are well within the time frame that surnames were adopted in Western Europe.
Tightly Related N/A N/A 1 1-2 1-2 Few people achieve this close level of a match. All confidence levels are well within the time frame that surnames were adopted in Western Europe.
Related 0 0-1 2-3 3-4 3-5 Your degree of matching is within the range of most well-established surname lineages in Western Europe. If you have tested with the Y-DNA12 or Y-DNA25 test, you should consider upgrading to additional STR markers. Doing so will improve your time to common ancestor calculations.
Probably Related 1 2 4 5-6 6-7 Without additional evidence, it is unlikely that you share a common ancestor in recent genealogical times (1 to 6 generations). You may have a connection in more distant genealogical times (less than 15 generations). If you have traditional genealogy records that indicate a relationship, then by testing additional individuals you will either prove or disprove the connection.
Only Possibly Related 2 3 5 7 8-10 It is unlikely that you share a common ancestor in genealogical times (1 to 15 generations). Should you have traditional genealogy records that indicate a relationship, then by testing additional individuals you will either prove or disprove the connection. A careful review of your genealogical records is also recommended.
Not Related 3 4 6 >7 >10 You are not related on your Y-chromosome lineage within recent or distant genealogical times (1 to 15 generations).

Taylor Family Genes interpretation

We depart from the above in some ways:

  1. Confidence in 12- & 25-marker matches

    With 0:12 or 1:25 matches ("Related"), we believe that insufficient genetic information is being compared and, therefore, do not have much confidence in the interpretation. We're not saying the interpretation is wrong, merely that it's doubtful. We are, however, more confident in the interpretations of 37 or more markers.
     
  2. Probabilities

    The FTDNA interpretations describe the most probable category of relatedness. However, they are not certainties; a particular match may depart from the most probable...
  3. Time Frame

    For assigning genetic families, we define the genealogical time frame as 24 generations. At an estimated average generation length of 27.5, this calculates to approximately 1350 AD, which year is thought to mark the beginning of universal surnames in England. The process is generally accepted to have been completed by 1400 AD.
  4. Marker Mutation Rates

    It is not only the so-called genetic distance which matters, but on which markers the genetic distance occurs. There is a wide variation in marker mutation rates; For example, CDY has an average mutation rate of 1:28, DYS385 has an average rate of 1:442, DYS392 is 1:1923 and DYS454 is 1:6250. A difference on DYS454 is more important than one on CDY.