Haplogroup

A haplogroup is a group of single chromosomes, or single DNA strands, which share a common ancestor. They have the same mutation in all versions. 
Haplogroups show deep ancestral origins dating back thousands of years.
In human genetics, the haplogroups usually studied are Y-chromosome (Y-DNA) haplogroups and mitochondrial DNA (mtDNA) haplogroups. Both can be used to define genetic populations. Y-DNA is passed only from father to son, while mtDNA is passed only from mother to children. Neither recombines, and thus Y-DNA and mtDNA change only by chance mutations with no intermixture between parents' genetic material.