Gill Family DNA Project

Frequently Asked Questions

How is the test performed?

Your genetic test kit consists of a cheek scraper and a collection tube. In about five minutes, you will be able to read the instructions and perform a painless cheek scraping. The effect of using the scraper is about the same as brushing your cheek with a soft bristle toothbrush. A backup scraper & tube is included to insure that a good sample is obtained by our lab. We intend that you use them both!

Then what happens?

After you have placed your order, a genetic test kit and instructions will be mailed to you. Upon its' return your genetic sample will be processed, and the results will be entered into our secure, private and confidential non-web-based genetic library. A comparison between your specific genetic markers and those of others in the database will then be performed and you will be notified if another person matches your results perfectly.

How far back can you determine a genetic link?

All genetic tests from Family Tree DNA will provide you a probability that you and another person, who have an exact match, will have your Most Recent Common Ancestor (MRCA) within a range of time backwards. Our 12 marker test gives you the following range: 14.5 generations (50%) likelihood & 48 generations (90%) likelihood. Using our new 25 marker test the 50% likelihood drops to 7 generations and the 90% to 19.8 generations.

Is my data confidential?

Unless you give permission to reveal your associated name and family tree history online I will not place your name with your testing group number. However, in the interest of the project, it benefits us all to at least have access to your marker data, regardless if you would like to stay anon or not in case you should like to be contacted by potential related relatives. This is entirely up to you and in no way will your privacy be compromised.

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?

Here are the times back to the MRCA (Most Recent Common Ancestor) when ALL the markers match. For example, with 25/25 (all 25 markers match), there is a 50% probability that the MRCA was no longer than 7 generations, and a 90% probability that the MRCA was within the last 23 generations. Compare these with 12 and 10 -- with 12 markers, there is a 50% probability that the MRCA was within the last 14.5 generations, while with 10 markers, there is a 50% probability that the MRCA was within the last 16.5 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

12 of 12

14.5

48

62

25 of 25

7

23

30.4

FamilyTreeDNA's 25 marker test points 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

394

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

12/12 match with US

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

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
12 of 12	14.5	48	62
25 of 25	7	23	30.4

Situation	DYS #												Result
	393	390	394	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	12/12 match with US

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