Understand DNA Testing for Genealogy

DNA testing may be just the thing to help to break down some of those “brick walls.”  DNA or DeoxyriboNucleic Acid is the molecule sometimes known as the blueprint of life.  It contains the genetic code that exists in each cell of our bodies and is found throughout nature in living things. 

All the lab needs is some of your body’s cells to analyze your DNA.  It is easy to get these by scraping the inside of your cheek with a special swab.

 Using DNA for Genealogy

• The laboratory examines the DNA sample and uses standardized protocols to create a "results" profile for that individual.
   
• A single DNA test is not that useful, but by comparing your results against other individuals' test results, we can determine if you share a common ancestor with a second sample. 
   
• DNA testing can confirm that two test participants share a common ancestor. Paper trails (pedigrees) are needed to find which ancestor, when, and where


• DNA testing can also be conclusive in proving that two individuals do not share a common ancestor.

There are three types of DNA testing done in genetic genealogy:

Y-DNA for Genealogy

• Only males can take this test, but females can test a male relative to represent her line.
• Males have one x and one y chromosome, while females have two x chromosomes and no y chromosome. The y chromosome is passed from father to son and is usually identical from father to son.   Only males carry yDNA.  Females do not have yDNA and cannot pass it on.
• So far, most of the focus for genealogy is on the use of yDNA in surname projects.
• Because males carry the yDNA of their surname ancestors, we can test them as representatives of their ancestors. Each man gets his yDNA from his father, who got it from his father…all the way back.
• Occasionally, over thousands of years, there is a mutation in the DNA.  Without these mutations, we would all have the same DNA and testing would not be useful.  These mutations have resulted in distinctive DNA profiles for different families. These mutations occur at intervals that are especially useful for genealogy and are the focus of yDNA testing in surname genealogy.  It is the mutations that result in a distinctive yDNA profile for a lineage.
• A single Y-DNA test is not that useful, but by comparing the numbers at the markers against other men’s test results, we can determine if a man shares a common ancestor with a second sample.
• More information about Y-DNA.

mtDNA for Genealogy

• Males or Females can take this test
• Females carry a specific DNA material that is useful in genealogy called the mitochondria, or mtDNA.  This is the material that surrounds the chromosomes.
• The mtDNA is passed from a mother to her children, essentially unchanged.  Both males and females inherit mtDNA from their mother, but only females can pass it on.  (If there were no changes, each person would have exactly the same mtDNA as "Eve" and with each other.)
• This test is only useful in testing the participant's mother's mother's .... mother's line.
• As this line changes names every generation, it is relatively difficult to track more than a few generations through genealogy.
• All people who share the same "common ancestor" will carry essentially the same mtDNA and receive tests results that are also essentially the same.
• More information about mtDNA.

Family Finder-- atDNA (autosomal DNA)

• Both males and females carry autosomal DNA, which is inherited from both your parents.
• Autosomal DNA is found on a non-sex chromosome.  Humans have 22 pairs of autosomal chromosomes and a pair of sex chromosomes (X and Y). 
• Linked blocks of DNA across the 22 autosomal chromosomes are matched between two people.  The degree of matching yields evidence for the relationship.
• If two people share identical segments of DNA, they may share a recent ancestor.
• The Family Finder test adds to the information provided by Y-chromosome DNA and mitochondrial DNA (mtDNA) tests. It allows you to trace your other lineages such as your father's mother's father and your mother's father's mother.
• The Family Finder program determines relationships for up to five generations.
• To find the genealogical connection with your match, you need to consult traditional genealogy records. These are birth, marriage, and death records. They also include documents like the census.
• More information about atDNA. 

  ---

Genetic Genealogy helps you uncover your roots! 

Here are the simple rules of DNA testing: 

1. Only males can take a yDNA test.  A man you are testing with yDNA must be directly descended from the (male) ancestor you are interested in researching - with no females between them (yDNA cannot pass through a female ancestor). Surname projects use yDNA testing.

2. A female can find a male relative to be yDNA-tested to represent her surname family line.  This can be a father or brother, but sometimes you will have to go back up the family tree and back down to find the right male.  This male must be descended, through males only, from a common male ancestor.

3. A male who is tracing a line that comes to him through a female ancestor will use the same method of going back up the family tree and down again for find a male who descends, through males only, from a common male ancestor.

4. Both males and females can take an mtDNA test.  A person testing with mtDNA must be directly descended from the (female) ancestor you are interested in researching - with no males between the test taker and ancestor being researched (mtDNA cannot pass through a male ancestor) Though not useful in a surname project, mtDNA testing tells you your deep ancestry for your maternal line and can help you find others who share a maternal ancestor. 

5.  Both males and females can take an autosomal (Family Finder) test which tests the DNA received from both sides and is most useful for recent ancestors (6 generations or less going back).

  Here are the benefits of DNA testing for the genealogist:

• Confirm or eliminate relationships.
• Focuses research to related families.
• Directs research into a geographic area.
• Directs research into a specific timeframe.
• Establishes country or region of origin.
• Confirms variant surnames are family.
• Identifies pre-surname migration.
• Strengthens weak paper trails.
• Avoids pursuing false connections.