DNA Testing for Genealogy

Ash Parker
Nov 17, 2019
3 min read

Traditional methods for researching one's family history have gotten a technological upgrade in recent decades. The ability to digitize and transcribe text into searchable indexes available in online databases and genealogy portals made family history research accessible to everyone. Today, consumer DNA testing goes further to uncover family lines and origins. Affordable at-home testing tied to major genealogy services provides fast and intriguing answers. As more people are tested, results and insights improve.

Though DNA testing is not a new technology, the science behind it may be unfamiliar. Commercial DNA testing for ancestry insights has been advancing for years. Understanding the science, current research landscape, and types of DNA testing is a good start for introducing DNA into your genealogy toolkit.

How is DNA Used in Genealogy?

DNA ( deoxyribonucleic acid ) is the blueprint for life. Inherited from mother and father, DNA strings are packaged within 23 paired chromosomes--22 of which are called autosomes and one pair are the sex chromosomes, consisting of two Xs for females and XY for males. The genetic information in DNA is replicated in all of our cells and establishes physical characteristics like eye and hair color, height, and facial features. In addition to cellular DNA, DNA is present in the mitochondria of the cell. DNA testing can be used to identify family connections and lines of ethnic ancestry by haplotype/haplogroup. Haplotypes are genetic markers that tend to be inherited together, and haplogroups are populations that share common genetic ancestors. Identifying relationship connections can solidify genealogical research or jump-start stalled research questions by connecting us to unidentified pedigrees.

Types of DNA Test

There are different tests that can provide different information.

Autosomal--the 22 chromosomes that are not sex-chromosomes are inherited from both parents; this testing can identify relations within several generations, though may not be exact, as not all chromosomes are passed down
xDNA--X chromosomes passed from mother to daughter or son can be used to identify common maternal ancestors
yDNA--Y chromosomes passed from father to son, can only be done on males and identifies the patrilinear (father's) genetic line
mtDNA--mitochondrial DNA passed from mother to all her children, identifies the matrilineal (mother's) genetic line

Autosomal DNA testing, while newer, is more common in commercial DNA testing and can identify family relations more accurately. DNA testing of yDNA and mtDNA is limited to single ancestral line and is commonly used to map haplogroup membership. Early on, identification of ethnic group membership was less accurate, but as more results are mapped, test results are refined and new information can be revealed.

DNA testing can provide clues to where our ancestors came from and direct links to other people with common ancestors. Genetic genealogy does not eliminate the need to research family history through other channels, but it can improve our accuracy and provide new research questions to follow. Family history research benefits from a variety of resources and DNA testing is a tool with which every family historian should be familiar. Check out these additional resources for further reading.