Small Font Medium Font Large Font

How Many to Test? 12, 37, 67 Markers?

With several levels of Y-DNA test being offered, how does one know which is the right one to choose? If I submit a sample to you for testing and you find that I match exactly with another person, how many generations ago did we have a common ancestor?

Is the 37-marker test not enough? Why the need for a 67-marker test?

Our motivation to offer a 67-marker test was two fold:

  1. Family Tree DNA wanted to ensure our customers that by testing with us they could obtain the highest resolution Y-DNA test in the world (like FTDNA clients may also obtain the highest resolution test on their mtDNA by taking our Full Genomic Scan, which looks at the entire mitochondria molecule).
  2. Several groups of families have still not been able to completely determine the relatedness of group members with our flagship 37 marker test. Therefore we see two main advantages of testing 67 markers over testing 37:
    • Y-DNA67 can further refine our estimate of how closely related two individuals are,
    • By using additional markers groups of related participants have a better chance of finding mutations which identify sub-branches in the family.

However, not all participants or projects need to test 67 markers in order to achieve their objectives.

Some projects will be able to achieve their goals with a 12, 25 or 37 marker test. Only if you are in a project and part of a subgroup of that project where you match, exactly or nearly exactly, to several others will you gain by upgrading to additional marker.

Our motto could be: test only what you need, upgrade only when necessary.

Here are the times back to the MRCA when ALL the markers match. Those numbers are based in the latest results of the mutation rate study conducted by the University of Arizona. For example, with 37/37 (all 37 markers match), there is a 50% probability that the MRCA was no longer than 2 generations, and a 90% probability that the MRCA was within the last 5 generations. Compare these with 25 and 12 -- with 25 markers, there is a 50% probability that the MRCA was within the last 3 generations, while with 12 markers, there is a 50% probability that the MRCA was within the last 7 generations.

Table 1.

Probability for Most Recent Common Ancestor (MRCA)
Number of matching markers 50% probability that the MRCA was no longer than this number of generations 90% probability that the MRCA was no longer than this number of generations 95% probability that the MRCA was no longer than this number of generations
10 of 10 16.5 56 72
11 of 12 17 39 47
12 of 12 7 23 29
23 of 25 11 23 27
24 of 25 7 16 20
25 of 25 3 10 13
35 of 37 6 12 14
36 of 37 4 8 10
37 of 37 2 to 3 5 7
65 of 67 6 12 14
66 of 67 4 8 9
67 of 67 2 4 6

FamilyTreeDNA's 37 and 67 marker tests point to a much lower number of generations to the most recent common ancestor than other commercially available tests. We use exacting statistics appropriate for the non-independent transfer of genetic material on the Y Chromosome.

Table 2.

Examples of previously tested individuals.
Situation DYS # Result
  393 390 19 391 385a 385b 426 388 439 389i 392 389ii  
 
California-Same Surname 12 22 14 10 14 15 11 15 11 14 11 31 12/12 match with Argentina
Argentina Same Surname 12 22 14 10 14 15 11 15 11 14 11 31 12/12 match with California
 
5 Generations in US-Same Surname 12 23 14 10 13 17 11 16 11 13 11 30 12/12 Match with E. Europe
Recent Arrival from E. Europe-Same Surname 12 23 14 10 13 17 11 16 11 13 11 30  
Houston Same Surname 14 22 15 10 13 13 11 12 11 12 12 29 Not a match with Brazil
Brazil Same Surname 13 25 16 10 12 14 12 12 11 13 11 29 Not a match with Houston
 
Nordic Genetic Fingerprint 13 23 14 10 14 14 11 14 11 12 11 28 Sample of Nordic Haplotype
 
Western Atlantic (Modal) Haplotype 13 24 14 11 11 14 12 12 12 13 13 29 Sample of W. Atlantic Haplotype
 
Samaritan 12 23 14 10 14 17 12 15 13 13 11 29 Sample of Samaritan Haplotype