For questions about using DNA to further knowledge of family history, relationships, ethnic origin, and overall ancestry. Most common tests include Y-DNA, mitochondrial DNA, and autosomal DNA.
dna is a high level tag for genetic genealogy questions, and sub-tags exist for each of the common DNA tests used for genealogical purposes. This tag should be paired, if applicable, with the tag for the specific test type tag to help clarify the question context.
mitochondrial-dna (commonly abbreviated mtDNA) is useful in genetic genealogy because it is a specific test for the maternal line of a family. It is only passed from mother to child; fathers do not pass any mtDNA to their children. This test provides maternal Haplogroups and shared marker matching.
y-dna is used in genetic genealogy to research the paternal line of a family. The Y-chromosome is only passed from father to son. Y-DNA testing includes Y-STR, Y-SNP, and Big-Y tests. This test provides paternal Haplogroups and shared marker matching.
autosomal is a test for researching both sides of the family up to five to eight generations, and also typically provides X chromosome results (which are not technically autosomes). Autosomal DNA, unlike Y-DNA or mtDNA, is passed on by both parents to their children. This test is also known as AncestryDNA, 23andMe, and the FamilyTreeDNA FamilyFinder test.
xdna results are typically included in autosomal tests, even though they are actually an allosome rather than an autosome. X-DNA is a sex chromosome that is passed from fathers to daughters, and from mothers to both sons and daughters.
haplogroup is to be used for questions about ancestral DNA research into specific haplogroups. Haplogroups are groupings of genetic markers that imply common ancestry hundreds or thousands of years ago.