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DNA Test & Genetic Testing

This blog is reposted from the clevelandclinic.org

Overview of genetic testing

What is genetic testing?

Genetic testing may also be called DNA testing. It’s a type of test that can identify changes in the genes, chromosomes or proteins in your body. Genetic testing takes a sample of your blood, skin, hair, tissue or amniotic fluid. The test may be able to confirm or rule out if you have a genetic condition. It may also help determine your chances of developing or passing on a genetic disorder.

What does genetic testing look for?

Genetic testing looks for changes in your genes, chromosomes and proteins. DNA tests can give you lots of information about the genes that make up who you are. They can confirm if you have or don’t have a specific disease. They can determine if you have a higher risk of developing certain conditions. And they can find out if you carry a specific mutated gene that you can pass to your child.

What are the different types of DNA tests?

The various types of genetic tests include tests that look at:

  • Genes: Gene tests analyze your DNA to find changes (mutations) in your genes that can cause or increase your risk of developing a genetic disorder. Gene tests may study one gene, a few genes or all your DNA. Looking at all your DNA is called genomic testing.

  • Chromosomes: Chromosomal tests study your chromosomes or long strings of your DNA. They look for changes in the order of genes that could be the cause of a genetic condition. One example of the changes looked for is an extra copy of a chromosome.

  • Proteins: Protein tests analyze the enzyme activity in cells, looking for the products of chemical reactions in our cells. Problems with your proteins can mean you have changes in your DNA that can cause a genetic condition.

Prenatal testing

Mutations in the genes or chromosomes in your developing baby (fetus) can be detected through a prenatal DNA test while you’re pregnant. Prenatal testing doesn’t test for all possible conditions. But it can determine the chances of your baby being born with certain conditions that we know how to look for. If your baby has an increased risk of having a genetic condition because of the family’s genetic history, your healthcare provider may recommend prenatal testing.

Diagnostic testing

Diagnostic testing can confirm or rule out specific genetic diseases or chromosomal problems. But it doesn’t test for all genetic conditions. Diagnostic genetic testing is often used during pregnancy, but it can be used at any time to confirm a diagnosis if you have symptoms of a certain disease.

Carrier testing

If a condition is autosome recessive, it means that someone can carry a gene for that condition but not have symptoms. Carrier testing can tell you if you carry a copy of a mutated gene for an autosomal recessive disease. This is generally done because one parent’s family has a history of a disease that is passed on in an autosomal recessive way, which means that it takes a copy of the gene from each parent. So if one parent knows they carry an autosomal recessive gene, the other should be tested so they know the risk of passing that disease to their kids.

Preimplantation testing

Preimplantation testing can find genetic mutations in the embryos that were made using assisted reproductive techniques (ART), like in-vitro fertilization (IVF). A small number of cells are taken from your embryos and tested for certain mutations. Only embryos without these mutations are implanted in your uterus to attempt to start a pregnancy.

Newborn screening

Your newborn will be tested two days after they’re born. A newborn screening tests for certain genetic, metabolic or hormone-related conditions. Newborns are screened immediately after birth so treatment can start right away if needed. States decide which diseases to screen for, but in the United States, hospitals can screen for more than 35 conditions in newborns.

Predictive and presymptomatic testing

Gene mutations that increase your likelihood of developing a genetic condition later in life can sometimes be detected through predictive and pre-symptomatic testing by looking for changes in your genes that increase your risk of developing certain diseases. These include certain types of cancer such as breast cancer. Presymptomatic testing can tell whether you’ll develop a genetic disorder before you’ve developed any symptoms, but not with 100% certainty. There is always a chance for errors when this type of testing is done, so speak with your provider about this before you do it.

What diseases can be detected through genetic testing?

It’s important to remember that while genetic testing can detect some conditions, it doesn’t detect everything. In addition, a positive result doesn’t necessarily mean you’ll develop a condition. But genetic testing can be useful to confirm or rule out many different diseases and conditions. These conditions include:

  • Down syndrome.

  • Huntington's disease.

  • Cystic fibrosis.

  • Sickle cell disease.

  • Phenylketonuria.

  • Colon (colorectal) cancer.

  • Breast cancer.

How does DNA testing work?

Your healthcare provider will collect a sample of your blood, hair, skin, tissue or amniotic fluid. Amniotic fluid is the fluid that surrounds your developing baby (fetus) during your pregnancy. Your healthcare provider will send the sample to a laboratory. At the lab, technicians will look for changes in your genes, chromosomes or proteins. The technicians send the test results to your healthcare provider.

What are the risks of genetic tests?

The physical risks of most genetic tests are small. Prenatal testing does carry a small risk of losing your pregnancy (miscarriage). This is because the test requires a sample of amniotic fluid from around your developing baby.

The greater risks of genetic testing are emotional and financial. If you receive unexpected results, you may feel angry, scared, depressed, anxious or guilty. In addition, genetic testing can cost anywhere from hundreds to thousands of dollars. Insurance may cover the cost of genetic testing. But it often depends on the type of test and the reason for the test.

Also, genetic testing doesn’t provide information about all possible genetic conditions and not all of them are 100% accurate. And they don’t necessarily tell you about how severe symptoms may be or when a certain genetic condition may develop.

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