Testing direct paternal line (Y-DNA)
As Y-Chromosome is a sex chromosome, which defines men, only men can be tested, as they inherit their father’s Y-chromosome. It is not recombined when passed from father to son, so it remains almost identical for thousands of years. What changes across generations is a number of short tandem repeats (STR) on certain places of the chromosome, which is delivered also as a result on a certificate of testing. Family Tree DNA has created a free public service YSearch.org so that people who have tested with different companies can compare their results. Testing of Y-DNA resulted in a large phylogenetic Y haplogroup tree, which starts with the so-called “Y-Chromosome Adam,” the most recent patrilineal ancestor of all people living today, who is believed to have lived 60,000 to 90,000 years ago.
One can order testing of 37, 67, 111 markers or the complete Y-chromosome. More markers are tested more accurate predictions can be made. Matches are delivered also for 12 and 25 markers (see table 6). Matches have got an indication of a genetic distance between you and your match, which is a probability of sharing the most recent common ancestor (MRCA):
- 0=exact match, MRCA might be 7 generations ago at 37 markers and 5 generations ago at 111 markers
- 1=one marker difference, MRCA might be 10 generations ago at 37 markers and 7 generations ago at 111 markers
- 2=two markers difference, MRCA might be 14 generations ago at 37 markers and 9 generations ago at 111 markers.
According to the first scientific results, the most common Y-haplogroups detected in Slovenian populations are: 
- Eastern European haplogroup R1a1a (M198), which occurs with 36.2% frequency, followed by
- Western European haplogroup R1b (M343) with 20.3%,
- South-eastern European haplogroup I2a1 (P37.2) including I2a1b (M423) with 12.9%, and
- Central European haplogroups I1 (M253) with 11.9%, and J2 (M172) with 5.3%.
 Andrej Zupan & Damjan Glavač (2013) Genetic structure of Slovenian populations by polimorfisms Z-Chromosome and mithohondrial DNA. Drevesa 20(2013)1, p. 4-15 http://www.hawlina.com/srd/genetika.pdf