Genealogy Search Tips

The Basics of DNA Testing

Reasons for DNA Testing

During the past year or so millions of people purchased DNA Tests because they thought they might learn something about their ethnic origins.

And some people purchased DNA tests because they wanted to compare their DNA test results with the DNA test results of others. Analyzing DNA matches with other individuals and comparing the shared DNA matches with others can help find new cousins and ancestors. "Genetic Genealogy" uses DNA test results to help determine the relationships among individuals.

And more and more people are purchasing DNA tests for health management reasons. With a better understanding of one's DNA an individual might be able to select options that will result in a healthier lifestyle.

What is DNA?

DNA is short for deoxyribonucleic acid, a molecule present in nearly all living organisms. It contains the biological instructions that makes each species unique.

Human DNA is composed of approximately 3 billion individual components that appear in two long strands in the shape of a "double-helix" - it has the look of a twisted ladder or spiral staircase. These two long strands are joined and held together by two nitrogenous bases, sometimes called the "base pairs", that are the steps on our twisted ladder or spiral staircase analogy.

The unique genetic instructions for each individual are determined by his or her base pairs. There are four different nitrogenous bases: adenine (A), thymine (T), cytosine (C) and guanine (G). These 4 bases are usually represented as the As, Ts, Cs and Gs and are sometimes called the DNA Letters and the DNA Alphabet.

Each individual receives DNA from his or her mother and DNA from his or her father. This means that an individual's inherited DNA consists of 2 separate DNA molecules each of which contains approximately 3 billion base pairs.

For a more expanded discussion of DNA see our discussion

Where is Human DNA?

Human DNA is inherited from an individual's mother and father. In the egg cell there is DNA from the individual's mother and in the sperm cell there is DNA from the individual's father.

A human's first cell is created by the fusion of the egg cell and sperm cell and this cell contains the DNA received from both of the individual's parents. The DNA from both parents is in the nucleus of the cell.

The initial cell divides and makes a copy of itself and then the two cells make copies of themselves - this copying process continues and eventually there are over 35 trillion cells in a human being.

With the exception of the sperm, egg and red blood cells, a copy of the DNA molecule received from an individual's mother and a copy of the DNA molecule received from an individual's father are in the nucleus of each of the individual's 35+ trillion cells.

Obtaining an Individual's DNA for Testing

Today most DNA testing companies use a small amount of saliva or a cheek swab provided by each individual being tested. Then the testing companies extract each individual's DNA from the cells in the saliva or cheek swab sample.

The typical testing company mails each DNA Test purchaser a package that contains a tube for the saliva or the material for the cheek swab. A return envelope addressed to the DNA testing Laboratory is also provided - so the individual being tested provides the saliva or cheek swab sample and then mails it to the DNA testing company's laboratory.

When the saliva or cheek swab sample is received the DNA testing company extracts the DNA from the cells and then begins its DNA Testing process.

Measuring and Reporting DNA Test Results

Once the DNA is extracted from the saliva sample, the analysis of the DNA begins. The goal is to measure or evaluate the DNA at the selected locations for the test.

The laboratory tests determine which nitrogenous base is at each of the locations selected for the test. Each nitrogenous base will be reported as an A, C, G or T, the first letters of each of the four bases, Adenine (A), Cytosine (C), Guanine (G) and Thymine (T).

The As, Cs, Gs and Ts discovered at the different locations will be used to prepare the reports for the DNA test and the reports will depend on the type of test. The 3 major DNA tests for ancestry are the Autosomal DNA test, the Y-DNA test and the mtDNA test.

To learn more about how DNA testing can provide ancestry information visit

For a more detailed discussion about each of the 3 ancestry DNA tests visit






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