DNA testing is constantly changing and improving. DNA testing is all about the size of the database. The more information it has to compare your information to, the better results you will get. Although a potentially powerful tool, DNA testing rarely provides an immediate answer. Traditional genealogical research is still necessary and important to connect generations.

International Society of Genetic Genealogy Wiki provides answers to common genetic genealogy questions.

DNAeXplained is a Genealogy News Blog that keeps up with all the latest developments with the various DNA testing companies.

What is DNA?
  • DNA is a complex molecule that is found in nearly every cell in our body.
  • DNA consists of two long chains of molecules joined together. The smaller molecules form pairs. These bonds and the order in which they are arranged determine personal traits such as eye color, hair color and height.
  • DNA testing looks at variations in a DNA sequence that builds a person’s genetic profile.
  • DNA in every human being is 99% identical. Only 0.1% of your DNA is unique.
  • Each parent gives their child exactly half of their DNA, but the assortment of genes or markers is unique to each child.
  • Tests sometimes refer to Centimorgan “cM”
    • cM is a unit of measurement. It helps predict how likely it is that two people share a recent common ancestor
    • cM’s are at the heart of genetic genealogy relationships
Types of DNA tests


  • Provides you with a breakdown of your genetic ethnicity by comparing your DNA with the DNA of those around the world. Genetic signatures help predict where ancestors once lived.
  • This test is not gender specific, it can access both sides of your family.
  • There is nothing in this test that will tell you which branch of your family a match is on. Therefore, having other family members tested will give you more information to work with.
  • Matches are based off of over 700,000 markers from your entire genome.
  • Testing companies provide the total amount of DNA – measured in centimorgans CM – shared with each genetic match. You can estimate a relationship based on the number of shared CM’s. A good chart to estimate relationships is available at Autosomal DNA Statistics
  • This test currently allows you to find cousins across any of your ancestral lines who shared an ancestor within the last four to five generations.
  • The greater the generational distance, the less likely it is that autosomal DNA will identify potential ancestors
  • Note: When looking at your ethnic results, a lack of results does not mean that you do not have any ancestors from that population, it just means that you did not inherit that particular gene marker.
  • Note: Clustering tools can be helpful to analyze autosomnal test results.


  • Looks at your direct paternal lineage through your Y chromosome.
  • Shows your paternal migration path from thousands of years ago.
  • Available only for males.
  • There are Y-DNA surname studies, which can help you identify potential ancestors.


  • Looks at your direct maternal lineage through your mitochondrial DNA.
  • Shows your maternal migration path from thousands of years ago.
  • Available for both males and females.
  • Mothers pass mitochondrial DNA to both male and female children, however only female children pass the mitochondrial DNA to their children.
Places to Test

Note: The size of the database is vital for DNA research. The larger the database, the more information the company can offer. This means that you have a greater chance of connecting to cousins and ancestors.

  • 23andme
    • Tests include: Y-DNA testing and mtDNA testing.
    • Now integrated with MyHeritage.
  • Ancestry DNA
    • Autosomal testing only.
  • DNA Ethnicity
  • DNA Gedcom
    • Allows you to upload raw data from Family Tree DNA and 23andme in order to compare your results to a larger database.
  • DNA.Land
    • DNA.Land is a relatively new service that offers analysis of raw data from 23andme, AncestryDNA and Family Tree DNA.
  • Family Tree DNA
    • Tests include: Y-DNA testing, mtDNA testing and family finder (autosomnal DNA).
    • Has the largest Y-DNA database in the world.
    • Only company to offer full mitochondrial sequence.
    • Offers free webinars.
  • GEDmatch
    • GEDmatch allows you to upload data from Family Tree DNA, 23andme and Ancestry to compare results.
    • Registration is free.
    • Contains a forum section where you can connect with other users.
    • Note: Law enforcement has recently begun using this database to identify suspects. Generally they enter DNA found at a crime scene and then use matches of close relatives to narrow down suspect pools.
  • Living DNA
    • This British site’s ethnic breakdowns include 21 regions just in Britain.
  • My Heritage
    • My Heritage now offers DNA testing through their website.
Tools to Analyze DNA Results

DNA Cluster Chart

  • The name along the side are DNA matches
  • The diagonal line shows where matches interset with theselves
  • Colored squares means two testers match you and eachother
  • Square clusters indicate shared ancestry
  • Grat boxes outside colored clusters indicate someone who belongs in both clusters
  • Clusters indicate different famiyl lines
  • Large clusters mean many descendats of that common ancestor have tested

DNA Match List

  • Organize match lists into group to help organize your research
  • Start by organizing into 4 groups – by great grandparent couples, or into 8 groups – by 2x great grandparent couples


Chromosome Maps

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