Southern California Genealogical Society DNA Project
Males pass Y-DNA only to their male children. The results of the Y-DNA testing are found in Y Results and are grouped first by Y-DNA haplogroups, then by matching groups. (For geographic description of Y-DNA Haplogroups see Results.) The locations on the Y-DNA chromosome are called markers and have names such as DYS390, DYS381, etc. The numbers represent repeats of patterns and are called allele repeats. Men who are in the same haplogroup and also have similar numbers of allele repeats are grouped to form family units. Those who have tested at ONLY Y-DNA12 or Y-DNA25 are encouraged to go to Order Tests and Upgrades and upgrade to either Y-DNA37 or Y-DNA67 so they can accurately be placed in their proper grouping.
Females pass mtDNA to all their children, but males cannot pass it to the next generation. Therefore, both males and females can test their mtDNA which comes from their maternal line. In mtDNA Results, the results are grouped in mtDNA Haplogroups (for geographical definitions see Results). HVR1 and HVR2 represent different areas of the mtDNA and the numbers listed indicate the mutation signature in each area. People with the same haplogroup and same sets of mutations in both HVR1 and HVR2 have a common ancestor, but since mtDNA mutations much more slowly then Y-DNA and people are less likely to know their straight female line back many generations, identifying and naming common ancestors is less likely with mtDNA than with Y-DNA.