What are DNA tests?

DNA tests, or genetic tests, look for changes (variations) in your genes, chromosomes and DNA. This is also called gene testing. DNA tests can give you lots of information about your genetic makeup. They can often:

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Confirm if you have or don’t have a specific disease

Determine if you have a higher risk of developing certain conditions

Find out if you carry a specific altered gene that you can pass on to your child

If you’re interested in gene testing, you should speak to a genetic counselor. They can help you decide if DNA testing is right for you, and if it is, which kind. They’ll also be able to help you understand the results.

Genetic tests may look at your genes, chromosomes and/or almost all of your genetic material, which is made up of DNA. Your healthcare provider will recommend certain tests based on several factors. These factors include your family history, medical history and any suspected genetic conditions.

Gene tests examine your genes to find changes that can cause or increase your risk of developing a genetic disease.

Gene tests include:

Targeted single variant: Single variant testing looks for a specific change (variant) in one gene that’s known to cause a particular disorder. Your healthcare provider may use this test to determine if a genetic abnormality running in your biological family is found in you.

Single gene: Single gene testing looks for any changes in one gene that’s known to cause a specific condition. Your provider may recommend single gene testing to confirm, or rule out, a diagnosis if you have symptoms of the condition or it runs in your family.

Genetic testing panel: Gene panels look for changes in more than one gene. Genetic testing panels are used when changes in any of several genes can cause one or more symptoms that are found in you.

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Large-scale genomic tests look for changes throughout your DNA. Your provider may suggest genomic testing if other gene tests haven’t found a genetic reason for a condition. Or they may recommend it if you have a complex medical condition.

There are two kinds of genomic testing:

Whole exome sequencing: Whole exome sequencing looks for changes in many of your genes.

Whole genome sequencing: Whole genome sequencing looks at more than just genes — it looks at most of your genetic material/DNA.

Chromosomal tests study your chromosomes — long strings of your DNA. This type of test looks for changes in your chromosomes instead of your genes. Chromosomal testing may find:

An extra copy of a chromosome

A missing copy of a chromosome

An added piece of a chromosome (addition)

A missing piece of a chromosome (deletion)

A rearrangement of certain segments of chromosomes (translocation)

When a gene within a cell is active (turned on), it means the cell goes through the process of reading instructions and assembling a protein that will be expressed as a certain trait or condition.

Gene expression tests study the activity level of active genes. Certain conditions, including many kinds of cancer, may occur when a particular gene is too active (overexpression) or not active enough (underexpression).

Gene testing has many valuable uses. They can offer important information about your DNA or the genetic background of a loved one. The uses of DNA tests include:

Your healthcare provider can detect changes in the genes or chromosomes of a fetus through a prenatal genetic test while you’re pregnant. Prenatal testing can determine the chance of your baby being born with certain medical conditions. If your baby has an increased risk of having a condition because of your family’s genetic history or because there are signs of a condition in the fetus itself, your provider may recommend this type of test.

Diagnostic testing can confirm or rule out specific genetic disorders or chromosomal problems. But it doesn’t test for all genetic conditions. Healthcare providers often use diagnostic testing during pregnancy. But they can use it at any time to confirm a diagnosis if you have symptoms of a certain disease.

If a condition is autosomal recessively inherited, it means that you can carry a gene for that condition, but not have symptoms. Carrier screening can tell you if you carry a copy of an altered gene for an autosomal recessive disease. If both parents are carriers for the same condition, there would be a 25% risk of passing that on to a child.

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Providers offer this testing to everyone planning a pregnancy or who is in the early stages of pregnancy. While some families know that they have a history of a disease that is passed on in an autosomal recessive way, others may not.

Preimplantation testing can find genetic changes in embryos made using assisted reproductive techniques (ART), like in vitro fertilization (IVF). Your provider takes a small number of cells from the embryos and tests them for certain changes. This way, you can make an informed choice about which embryos your provider will implant in your uterus to start a pregnancy.

Newborn screening tests for certain genetic, metabolic or hormone-related conditions. Healthcare providers screen all newborns immediately after birth so treatment can start as soon as possible if they need it. In the U.S., hospitals can screen for up to 80 different medical conditions. Each state decides which diseases to screen for in newborns.

Your healthcare provider can sometimes use predictive and pre-symptomatic tests to look for genetic changes that increase your likelihood of developing a condition later in life. These include certain types of cancer. Genetic predisposition tests like BRCA testing look for mutations in the BRCA genes. Mutations in these genes can mean an increased risk of breast cancer and other cancers.

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Pre-symptomatic tests can tell whether you’ll develop a genetic disease before you’ve had any symptoms. But not always with 100% certainty. So, speak with your provider about the risks and benefits.

Pharmacogenomics is a type of testing that looks for changes in your genetic makeup that may affect how your body processes certain medications. The test determines if a medication will work for you. If the test shows it will work, it can also predict the safest and most effective dose. This helps your healthcare provider choose the best treatment options for you.

It’s important to remember that while gene testing can find some conditions, it doesn’t detect everything. Also, a positive result doesn’t always mean you’ll develop a disease. But DNA tests can be useful to confirm or rule out many different diseases and conditions. These conditions include: