How to Read DNA Test Genealogy

by Lynda Altman

Genealogical DNA tests will tell you how your DNA compares with other individuals who have taken the same tests. Females take a mitochondrial DNA test, or mtDNA, and males use a Y-chromosome DNA test. The results for both tests are read in the same manner. The DNA test results will be a series of four letters: A, C, G and T. These letters are repeated in a specific sequence called a DNA sequence. The DNA test results will show your unique sequence printed out on an easy-to-read form.

Reading a Genealogy DNA Test

Read the test results. The results will indicate how your DNA compares to the Cambridge Reference Sequence (CRS), which is the human genome without mutations. DNA nucleotides are represented by the letters A, C, G and T. Your particular genealogy is determined by comparing the sequence of your test to the CRS. Depending on how the letters are arranged in your DNA, a haplotype is assigned. Individuals with the same DNA patterns have the same haplotype.

Determine where your DNA deviates from the CRS. Your test will show you the deviations by highlighting where they occur. The most common deviation is when a substitution or transition occurs. For example, a C is replaced by an A, T or G. A transversion is another common deviation. A transversion occurs when a C or a T is replaced by an A or a G, or the other way around. The least common type of mutation is where a nucleotide is added or missing.

Decide which family line you will trace using the genealogy DNA test results. Women will follow their maternal line, as mtDNA traces a woman to her mother, her mother's mother, and so on, as the mtDNA is passed from mother to daughter. Men will trace their paternal lineage through their father, their father's father, and so on. The Y chromosome is passed from father to son. Women do not have a Y chromosome.

DNA chain

Compare the results of your DNA to other individuals with the same haplotype who share similar places of origin or who have the same surname. The company that supplied you with the genealogy DNA test will give you information on how to access other people with similar DNA. Reputable DNA testing companies will have a way to contact them if you have specific questions about your test results.

Items you will need
  • Genealogy DNA test results

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