In human genetics , the haplogroups most commonly studied are Y-chromosome ( Y-DNA ) haplogroups and mitochondrial DNA ( mtDNA ) haplogroups , both of which can be used to define genetic populations .
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 .