Ginny’s Genealogical Gems
DNA as a tool for Research
There is a growing interest in DNA as a tool for genealogical research. Understanding your genes may help you further your family history and open several areas of investigation.
DNA research is based on the fact that every human being is born with 46 chromosomes. Gender is determined by chromosomes consisting of an X from the mother and either an X or Y from the father. If a child has an X from the father, she is female and if they receive a Y the child is male.
Information in the Y chromosome (Ycs) passes mostly unchanged from father to son for generations. Analysis of this genetic information in living people can help you determine whether you share a common paternal ancestor with another living person. Based on the number of genetic markers shared with another person, you can estimate how many generations in the past your common paternal ancestor lived. Ycs testing can help in verifying a common paternal ancestor, or learn about the origin of a particular surname. While only males carry the Ycs, a woman can have a male relative tested on her behalf to obtain this information.
In addition, each human being carries a genetic molecule in their cells called the mitochondrial DNA (mtDNA). This genetic component is found in the mitochondria, and is inherited exclusively along the mother’s side. Both males and females carry mtDNA, but only women pass their mtDNA to their children. MtDNA is helpful in verifying the existence of a common maternal ancestor or to study the ancient origins of our maternal line.
A third option is autosomal DNA which is shuffled at each generation and only half of it is passed to our offspring. It does not follow a direct path of inheritance as does the Ycs and mtDNA described above. However, current testing provides a survey of one million or more sites on a person’s nuclear genome. This information is helpful in identifying recent cousins within the last five generations, or the ethnic origins of your family tree. Companies like 23andMe, Family Tree DNA, and Ancestry all offer autosomal testing for genealogical purposes. Each company offering these tests has tutorials on their website to help with the interpretation of your results. Though these DNA tests do not provide you with a definitive pedigree, they do give specific direction to your research and contact information for living relatives.