While 99% of our DNA is the same among everyone, that 1% can mean a lot of variations in a person. It’s what determines our eye and hair color, our predisposition for diseases or illnesses and even a love or hatred of certain foods. These genetic differences or mutations are known as alleles.
Alleles can be dominant or recessive. Many of us are familiar with some dominant versus recessive alleles, such as brown (dominant) versus blue (recessive) eyes. If you mom has blue eyes and your dad brown, it’s more likely that you ended up with brown eyes because only one copy of the dominant allele is needed to show their effect. However, a parent may have two copies of the recessive allele for blue eyes, which is how you may have blue eyes, even if one of your parents had brown eyes.
Beyond eye color, a person may also carry illnesses or diseases, even if he or she doesn’t have the illness or disease.
What is a Genetic Carrier?
Every person carries two copies of most genes—one from each parent. Also known as a hereditary carrier or carrier, a genetic carrier is an individual who has a mutation in one copy of a gene. While, as a carrier, the person doesn’t have the disease associated with the mutation, he or she may pass this mutation on to his or her children, as a carrier has a 50% chance of passing the same mutation to the child.
For soon-to-be parents, this can be worrisome because a carrier doesn’t necessarily know if he or she carries a genetic condition, as there may be no symptoms of the disease. However, if both parents discovered they were carriers for the same genetic disease, their child would have a 25% chance of inheriting both copies of the mutation, thus leading to the development of the genetic disease.
For the most part, everyone carries a gene for at least one genetic disease. What’s more of a concern is if both parents have the same mutation. However, it’s important to note that there are a few conditions that can be caused by a mutation in just one set of DNA, as opposed to a set from each parent. Huntington’s disease is just one example.
While there are a number of genetic disorders, some of the more common genetic diseases include:
- Down syndrome
- Sickle cell anemia
- Cystic fibrosis
- Marfan syndrome
- Duchenne muscular dystrophy
- Spinal muscular atrophy
- Tay-Sachs disease
- Fragile X syndrome
How Does a Carrier Screening Work?
Genetic carrier screening is a test to determine if an individual is a carrier for certain genetic diseases. Through a blood or saliva sample, a lab can check for genetic mutations associated with diseases and conditions. While DNA testing can provide insight into your health history, it’s not foolproof. There’s always a small chance that one can test negative but actually be a carrier.
Often, one parent will be tested first. If that parent’s tests are positive, then the second parent would undergo testing to see if they share any of the same genetic mutations. If one or both parents test negative, their child will not inherit the genetic disease. However, if both parents are carriers for the same genetic disease, their child has a 25% chance of inheriting the condition. Some parents may choose to move forward as planned, while others may explore other options, like IVF (using sperm and/or an egg from someone other than the parents) or adoption.
Who Should Receive a Carrier Screening?
Many soon-to-be parents want to know if their future children would be at risk for inheriting certain genetic diseases. In the past, carrier screening was only recommended by doctors for at-risk individuals (people who are more likely to carry specific genetic mutations). For example, people of Ashkenazi Jewish, French-Canadian and Cajun descent are more likely to carry the genetic mutation for Tay-Sachs disease, while African Americans, Greeks, Turks and Italians have an increased risk of sickle cell anemia and thalassemia.
However, as of 2017, The American Congress of Obstetricians and Gynecologists (ACOG) recommends all women to be screened for cystic fibrosis and spinal muscular atrophy and to receive a complete blood count to screen for a risk of hemoglobinopathies, a genetic defect that can result in sickle cell anemia and thalassemia.
There are a number of ways to receive carrier screening. The Pathway Genomics Carrier Status DNA Insight® test screens for more than 120 recessive genetic diseases, including ACOG-recommended conditions, Ashkenazi Jewish conditions and other conditions. Through Carrier Status DNA Insight, patients can gain knowledge on their risks of passing inheritable genetic diseases to their children or future children. Speak with your doctor to determine the appropriate testing option for you.