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Y-DNA Test Specs

3 types of DNA hold clues to your family connections

The Y-Chromosome (Y-DNA) is a sex determining marker that is found in males. Male individuals have one Y-Chromosome and one X-Chromosome (XY), whereas females have two X-Chromosomes (XX). Y-DNA is unique because it is inherited in a strict paternal fashion from father to son. Thus, an individual's Y-DNA is the same or very similar to his father's Y-DNA and the Y-DNA of all of his forefathers. Likewise, any individuals who are descendents from the same paternal lineage will share exactly the same Y-DNA. The Y-DNA is often considered as the most reliable marker of male biological lineage as every male family line is characterized by a distinct Y-DNA type and the Y-DNA type of a family is a remarkable marker to search for and re-unite males who have descended from the same paternal lineage.

The Y-DNA contains two types of genetic markers that provide useful family lineage information: STRs and SNPs. SNPs are slow mutating markers used to study "deep ancestry" or "haplogroups" tracing back tens of thousands of years. STR markers are fast mutating markers that are used to trace "recent" ancestry from the past few hundred years. The fast mutation rate of STR marker makes it ideal for family searches to look for long lost paternal family lines.

When a Y-DNA STR marker test is performed, a panel of STR markers are tested on the Y-DNA to examine the number of repeat "alleles" at each Y-DNA locus. Since all males who descended from the same forefather have the same or very similar Y-DNA STR profile (haplotype), Y-DNA STR markers will allow you to search for male family members who shared the same paternal ancestor as you within the last 150 generations. Once a match is found, the Y-DNA profiles between the two matching individuals can be compared to estimate how long ago they shared a common male ancestor.

Lineage traced: Paternal line (father's, father's, father's line)

Strengths: Can estimate the number of generations ago that two males shared a common paternal ancestor.

Limitations: Can only trace male relatives who descended from the same paternal line (father's father's father...). Cannot trace other lines, such as descendents from the mother's father's line, or the father's mother's line. Will not tell you your relationship type.