Building upon the basic terminology of DNA, you will want to find those closely related to you. FTDNA will provide you with matches and you will notice "genetic step distance" of each match. As previously discussed, 12 marker tests will only provide haplogroup. You may be an exact match to many folks with different surnames at this level of testing as they are in the same haplogroup. This is why our base level of testing is 37 makers and in many cases we need 67 to isolate subclade or haplotype.
This is not an exact science and one size does not fit all. There are variations that apply to each unique sequence. Since mutations occur randomly they may appear in consecutive generations or may not happen in 20 generations. Mutations may move up or down. There are also multi step mutations to consider. Mutation rates are calculated by algorithm and are an average of when polymorphisms may occur. Keeping this in mind, let's explore the variations most often found in faster changing alleles. Most charts identify these alleles with a red highlight for your convenience.
Let's identify the "fast changers" in the first 37 markers:
First panel (1-12) DYS# 389a, 389b* and 439
Second panel (13-25) DYS# 449 and 464a, b, c and d
Third panel (26-37) DYS# 576, 570, CDYa and CDYb
*389a and b may reverse positions. For example a value of 11-12 may reverse to 12-11. The exact position is impossible to ascertain. This reversal is not considered a mismatch. This is also the case for DYS# 459, 464 and YCAII.. It is not possible to determine the exact order.
A 37/37 match means you are closely related to this participant sharing the same surname or variant. The probability of time to most recent common ancestor is 50% in 5 generations and 90% in 16 generations. The 50% likelihood in 5 generations is because mutations occur randomly. On average a mutation rate of 0 - 3 can be expected in 5 generations. Contact with these individuals and comparison of paper trails is essential to confirm the exact generation of common ancestor. Very few achieve this level of match.
A 36/37 match means you are related to this participant sharing the same surname or variant. Your mismatch most likely occurred at DYS# 576, 570, CDYa or CDYb. I have personally witnessed a genetic distance of 5 steps at CDYb between confirmed fourth cousins. Both participants shared a common third great grandfather. Testing of their fathers revealed the mutation was five steps at CDYb in one generation. The mentioned alleles are multi copiers and fast movers: CDY is the most volatile. This is why you should explore four and five step distances with the same surname or variant. Very few achieve this level of match.
A 35/37 match means you may be related to this participant sharing the same surname or variant. One of your mismatches may have occurred in the first 25 markers and you probably matched 24/25. Refer to the "fast changers" above as it is most likely as mismatch occurred at one of these alleles. If the two mismatches occur in the first panel it is not likely you are related. This will push back the time to most recent common ancestor but is still within the 24 generation time frame.
A 34/37 match means you may be related to this participant sharing the same surname or variant. If 2 of the mismatches occur in the first panel it is unlikely you are related. Comparison of other "fast movers" should be observed. This participant may be related in the 24 generation time frame.
A 33/37 match means you share the same surname or variant. Still check at CDYa and CDYb to rule out a multi step mutation. Most times, two of the mismatches are in the first panel and the participant is probably not related. Paper trail comparison is the only way to confirm or reject this match.
The same holds true for 67 marker tests. There are no "fast changers" in the fourth panel (38-47), five in the fourth panel (48-60) at DYS# 413a and b, 557, 481 and 446; zero in fourth panel (61-67).
A 67/67 match means you are closely related to a participant with the same surname or variant. The percentages increase to 50% in 3 generations and 90% in 5 generations. Very few will achieve this level of match.
A 65-66/67 match means you are related to a participant with the same surname or variant. The only exception is if the two mismatches occur in the first panel of twelve. Examine the fast changers and look for multi step mutations. Very few will achieve this level of match. The confidence level the participant is related is very well within the time frame of emergence of surnames.
A 63-64/67 match means you are probably related to a participant with the same surname or variant. Again the first panel of 12 is very important. Again check the fast changers listed. There is still a good chance this participant is related within the time frame for emergence of surnames.
A 61-62/67 match means you are possibly related to a participant with the same surname or variant. This type of match will be on the threshold of time frame for emergence of surnames.
Matches below 32/37 and 60/67 are considered most likely not related even within the same surname. Allele position of mismatch should be considered. Examination of paper trail and the possibility of multi step mutation place these matches within the realm of possibility though not probable.
Clan Forrester Society
DNA Research Coordinator