human Y-chromosome or simply yDNA
This is a partial screen scrape from Wikipedia that will give you good information if you are just getting started with Genetic Genealogy focused on human genetics of the male line or simply understood as the human Y-chromosome. A yDNA haplogroup is a haplogroup defined by mutations in the non- recombining portions of DNA from the male-specific Y chromosome which I say yDNA versus Y-DNA to be consistent in common nomenclature. Many people within a haplogroup share similar numbers of short tandem repeats (STRs) and other types of mutations called single-nucleotide polymorphisms (SNPs) which one must examine if they truly desire "to know for certain" of which line they descend in fact, not in mystery or even a rouse. The human Y-chromosome accumulates roughly two mutations per generation. yDNA haplogroups represent major branches of the Y-chromosome phylogenetic tree...
