When talking about two or more Y-chromosome STR (short tandem repeat) haplotypes, genetic distance is the total number of differences or mutations between two sets of results. In general, it is found by summing the differences between each STR marker.

For example, kit B291 and B125 have allele values of 29 and 28 respectively at DYS389II. This is a difference of 1 (29-28= 1). Because this is the only difference in their Y-DNA12 profiles (haplotypes), their genetic distance is 1.

Example: Genetic Distance = 1
Kit Surname Hg D
Y
S
3
9
3
D
Y
S
3
9
0
D
Y
S
1
9
D
Y
S
3
9
1
D
Y
S
3
8
5
D
Y
S
4
2
6
D
Y
S
3
8
8
D
Y
S
4
3
9
D
Y
S
3
8
9
|
1
D
Y
S
3
9
2
D
Y
S
3
8
9
|
2
B291 Didmoe L 12 23 14 10 17-18 11 12 11 12 14 29
B125 Didmoe L 12 23 14 10 17-18 11 12 11 12 14 28
B322 Ditmee L 12 22 13 10 17-18 11 12 10 12 14 29

In this example, kits B291 and B322 have differences at DYS390, DYS19, and DYS439. The difference for each is calculated (DYS390: 23-22= 1, DYS19: 14-13= 1, DYS439: 11-10= 1). The differences are added together. The total number of differences the Y-DNA12 haplotypes is 3 (1+1+1= 3). Their genetic distance at 12 STR markers is then 3.

Example: Genetic Distance = 3
Kit Surname Hg D
Y
S
3
9
3
D
Y
S
3
9
0
D
Y
S
1
9
D
Y
S
3
9
1
D
Y
S
3
8
5
D
Y
S
4
2
6
D
Y
S
3
8
8
D
Y
S
4
3
9
D
Y
S
3
8
9
|
1
D
Y
S
3
9
2
D
Y
S
3
8
9
|
2
B291 Didmoe L 12 23 14 10 17-18 11 12 11 12 14 29
B125 Didmoe L 12 23 14 10 17-18 11 12 11 12 14 28
B322 Ditmee L 12 22 13 10 17-18 11 12 10 12 14 29