You should test more Y-chromosome DNA (Y-DNA) STR (short tandem repeat markers when you want to compare additional markers against others with similar results. Our motto could be: Test only what you need, and upgrade only when necessary.
Time to Most Recent Common Ancestor (MRCA)
| Number of matching markers | Probability that the MRCA was not more than this number of generations ago |
|---|
| 50% | 90% | 95% |
|---|
| 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 |
| 107 of 111 |
7 |
11 |
13 |
| 108 of 111 |
5 |
10 |
11 |
| 109 of 111 |
4 |
8 |
9 |
| 110 of 111 |
2 |
6 |
7 |
| 111 of 111 |
1 |
3 to 4 |
5 |
Additional STR markers will refine your matches. If you currently have many Y-DNA12, Y-DNA25, Y-DNA37, or Y-DNA67 matches you should certainly consider upgrading your Y-DNA profile to a higher level.
The level that you choose and the need to upgrade depends on:
- Your goals
- The amount of testing already completed by others in a group project that you are joining
- The degree of certainty for a relationship (match) that you desire.
For genealogical matching, the most important factor is the degree of certainty that your near or exact matches are indeed related to you in recent generations. Family Tree DNA offers several levels of testing for our Y-DNA tests. The table on the right shows the time to a common ancestor for near and exact matches at different Y-DNA testing levels.
Generally, testing additional STR markers will:
- Narrow the expected time to a common ancestor with an exact match
- Increase the degree of certainty for a near or exact match
- Reduce the number of irrelevant matches
You may always upgrade to a higher level of testing as your number of matches and needs change.