FAQs — General Information about DNA and DNA Testing

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1. What is DNA?
2. Can DNA be changed?
3. For what purposes do people use DNA testing?
4. How is DNA testing done?
5. How does the testing process work?

1. What is DNA?

DNA, which stands for deoxyribonucleic acid, is the genetic material found in all living things. It controls how our bodies function and what characteristics we inherit from our biological parents.

We inherit our DNA in equal portions from our biological mother and father. Therefore, we share 50% of our DNA with our mother and 50% with our father. Full biological siblings (children sharing the same biological mother and father) also share much of their DNA with each other. To a lesser degree, we also share DNA with other relatives such as our aunts, uncles, and cousins.

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2. Can DNA be changed?

In general, DNA does not change. Environmental factors, such as excessive exposure to ultraviolet radiation and cancer-causing agents, might cause a few changes in DNA, which happen only in small areas of the body. Most of the time, these changes do not affect DNA test results.

DNA from peripheral blood also can be changed with a bone marrow transplant, but DNA in other body tissues remains the same. Drugs, alcohol, or diet will not affect the test.

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3. For what purposes do people use DNA testing?

DNA testing can be used to answer questions about family relationships. These questions often become important for persons making decisions concerning child support, inheritance, adoption, and health care. DNA testing can be used to:

• Identify a child’s biological father so that child support can be legally enforced
• Give a child the emotional support of knowing his/her biological father
• Satisfy curiosities about family relationships
• Help adoption agencies verify the biological parents of a child
• Assist adoptees in finding biological family members
• Verify inheritance rights
• Help immigration authorities reunite families
• Determine whether twins are fraternal or identical
• Help grandparents identify their grandchildren

DNA testing is also used in the medical field to help health professionals diagnose, prevent, or treat inherited diseases.

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4. How is DNA testing done?

A DNA test starts with sample collection. DNA may be extracted from almost any part of the body, but the most common method is the painless buccal/mouth swab—a cotton-like swab rubbed against the inner cheek of a patient to collect loose cheek cells.

In the laboratory, scientists use different procedures depending on what questions need to be answered. In most DNA tests (paternity, grandparentage, siblingship), a procedure called the polymerase chain reaction (PCR) is performed to create a DNA profile for each person tested. This DNA profile is like a “snapshot” of a person’s DNA. Scientists run statistical analyses that compare two or more persons’ DNA profiles to determine if they are related. Those who are biologically related have specific similarities in their DNA profiles.

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5. How does the testing process work?

The DNA testing process can be broken down into the following five steps: 

1. Sample Collection.  DNA testing starts with sample collection. In most cases samples are collected by using a buccal (cheek) swab, a cotton-like swab rubbed against the inside of a patient’s cheek to gather loose cells. When samples reach our lab, we divide the samples to perform the test twice separately, ensuring accuracy of results.  

2. DNA Extraction. We use special chemical agents to extract and purify DNA from the buccal swabs. This procedure also separates DNA from other materials found in the cells.  

3. PCR. We use the Polymerase Chain Reaction (PCR) to create a DNA profile from each person’s sample. Each sample is placed in a thermal cycler (PCR machine) along with 16 fluorescent primers. These primers detect specific "loci" or locations on the DNA. During PCR, the thermal cycler takes the DNA sample mix through 30 cycles of heating and cooling. This molecular xeroxing process makes about one billion copies of each DNA loci.

4. Capillary Electrophoresis. The replicated DNA from PCR undergoes capillary electrophoresis. This process creates a “map” of the DNA loci produced from each sample. This map is called a DNA profile.  

5. Statistical Analysis. DNA profiles from the tested parties are then compared by a trained, experienced Ph.D. to determine if there is a biological relationship among them. In an inclusion case (the alleged father is the biological father), half the child’s DNA profile will match the mother’s and half will match the father’s. If 3 or more of the child’s loci do not match the alleged father’s, he is excluded (he is not the father).

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