Article by Shannon Wieloch
Last month we posted a blog on helpful tips to know before taking a DNA test. In part II of this topic, we delve deeper into the types of genetic testing commonly available to help you decide what type of testing may be right for you.
Some genetic tests inform you about your ancestry. Other tests provide you with information about your disease risk, health traits, response to medication, or if you carry a genetic change that could impact the health of your children. Some comprehensive tests provide all of this information.
Selecting the right genetic test depends on your specific interests and how you intend to use the results. Let’s explore different genetic testing categories.
Your ancestry, or ethnicity, describes the origins of your family. Clues about your ancestry come from genetic variants, or changes, in your DNA. Each ethnic group has variants that are more common to that group than another. Genetic testing companies can estimate your ancestry by comparing variants from people of different ethnicities.
Companies use a process, or a specific set of rules, to calculate ethnicity. NOTE: Each testing company uses different rules based on large sets of data, so companies may report different ethnic interpretations.
Ancestry is about more than the country your family came from. It may also provide information about your health since some medical conditions are more common in certain ethnicities. For example, people of Ashkenazi Jewish descent have a higher likelihood to carry a genetic variant associated with some hereditary cancers. This doesn’t mean that a person with this heritage will eventually develop these cancers. However, this information, along with other clinical information, may help you and your physician make decisions about cancer screening.
Alzheimer’s disease, cancer, depression and heart disease are common conditions. Many people hope that genetic testing will predict if they’ll develop these conditions, but more than just genes affect your disease risk; lifestyle choices also make a difference.
Genetic testing companies may tell you if you have a genetic variant that can increase your risk for a particular condition, but no company will be able to give you an exact risk for any disease. This is because research into the potential impact of genes on health is still emerging. Scientists are still trying to better understand how genetic variants may work together or with environmental factors to cause disease.
For some conditions, lifestyle choices can have a big impact while gene variants play a smaller role. For other conditions, it’s the reverse. But remember, even when it is the latter, genes are not destiny. You can often lower your risk by leading a healthy lifestyle.
Genes can influence how we react to medications. This area of genetics is referred to as pharmacogenomics.
While most people respond to medications as expected, the same dose of the same drug can either have little effect or cause serious side effects in other people. In both cases, genetic variants may be the cause.
Pharmacogenomics may help your health care provider determine the best medication and dose for you. Not all differences in drug response are due to genetic variants though, so be sure to talk with your healthcare provider before making changes to your medications!
One person’s DNA is 99.9% the same as any other person’s; variants in that 0.1% are what make you unique!
A health trait is a distinguishing quality related to your well-being, such as how you digest dairy products or your response to alcohol. Most health traits have a complex inheritance, meaning that both genetic and environmental factors impact a person’s risk to develop a condition. For example, those with lactose intolerance never have an issue unless they eat dairy foods.
For the most part, these differences aren’t health concerns. Think of them as quirks that make you “You”. However, it can be helpful to know about these differences to avoid unnecessary discomfort.
You have two copies of almost every gene, one copy from your mom and one from your dad. Genetic variants can cause genes to malfunction, changing biological process within your body.
Many genetic conditions only affect a person if they get a non-working copy of a gene from each parent. That form of inheritance is called autosomal recessive. Examples of this type of inherited condition include cystic fibrosis and sickle cell anemia.
When a person has one non-working copy, they do not tend to show signs or symptoms of the condition associated with that gene. This is because the other copy works well enough to make up for the copy that has the genetic change in it. This person is referred to as a carrier.
Carrier screening looks for certain genetic changes in specific genes that fall into this category. We are all carriers of many recessive conditions. People of certain ethnic groups have an increased risk to be carriers of specific genetic conditions. For example, French Canadians have a higher chance to be carriers of Tay-Sachs-disease.
You are at an increased risk to have an affected child if both you and your partner are carriers of the same genetic condition. Knowing this information can be helpful in understanding your reproductive risks and options.
Genetic testing can offer a lot of information. It’s best to know what you want, and what information a test provides before you order any test.
Talk with your health care provider for more information about genetic testing. You may also want to talk with a genetic counselor, a health professional who is trained in genetics and can help explain your genetic testing options and how results may help guide your health care.
Want to learn more about genetics and how it can affect your health? Explore Mayo Clinic GeneGuide™, a genomics educational app.
Join us for Individualizing Medicine 2019 Conference: Precision Cancer Care through Immunotherapy and Genomics on Sept. 20-21, in Scottsdale, Arizona.
The conference brings together experts from Mayo Clinic and across the country to present and discuss case-based approaches to using genomics and new immunotherapies that oncologists and their teams can bring back to their own patients.
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Shannon Wieloch, MS, LCGC is a Mayo Clinic genetic counselor supporting the Center for Individualized Medicine.
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