What It Means to Be a “Carrier” of a Genetic Disease
By: Brian Hoeflinger, MD
May 11, 2025 | #46
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Disclaimer: Opinions are my own. Not medical advice.
Medical Trivia of the Week
Which organelle contains its own DNA and is inherited exclusively from the mother? (the correct answer is at the end of this email)
- A) Mitochondria
- B) Nucleus
- C) Ribosome
- D) Endoplasmic reticulum
Genetic Mutations and Inheritance
A genetic mutation is a change in the sequence of your DNA. DNA is found in every cell of your body, and your DNA gives every cell the information to perform its functions. A genetic mutation changes the information that your cells need to form and function properly. If your DNA is mutated, then you might experience the symptoms of a genetic condition yourself. But, possibly more importantly, you will pass this mutant DNA information on to your children. Just as eye color, hair color, and blood type are passed on from parents to their children, a life-altering genetic condition can just as easily be passed on too.
Being a carrier of a genetic disease means you have a copy of the gene mutation that causes the condition but you don’t have the disease itself. You have one copy of the mutated gene and one normal copy, and the normal copy usually masks the effects of the mutation so you are healthy. But you still can pass this genetic information down to your children.
Some genetic conditions have dominant inheritance, with a 1 in 2 chance of your child having the disease, and some have recessive inheritance, with a 1 in 4 chance. In the case of dominant inheritance, you having one copy of the mutated gene can cause the disease, and this mutation and disease can be directly passed on to your children by you alone. On the other hand, a recessive mutation requires two copies of the gene mutation to cause the disease, and both the mother and father would need to each pass the gene mutation to their child for the disease to be expressed. Therefore, if both parents are carriers of the same genetic condition, then their children have a 1 in 4 chance of inheriting two copies of the mutated gene (one from each parent) and a 25 percent chance of developing the disease.
In Partnership with Nucleus Genomics
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- Empowering Information:
Armed with the knowledge from your genetic test, you and your healthcare provider can develop a comprehensive, personalized plan that focuses on early detection and prevention. This proactive approach is designed not only to manage risk but also to provide peace of mind.
- DNA is the foundation of your health: Understanding your genetic predispositions can help inform every other health choice.
- Knowledge is power: Taking a proactive approach to your health is the best investment you can make. In the long run, it could save you thousands in medical bills, and possibly even your life.
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Carriers of recessive genes typically do not have symptoms caused by the disease, and as such do not know they are carriers unless they are tested genetically or the condition shows up in their children, which at that point is too late.
Cystic fibrosis, hemophilia, sickle cell disease, Down syndrome, and some cancers are all examples of genetic recessive disorders that can be passed on if both healthy parents are carriers of the disorder.
Standard genetic testing can be quite important when planning a family. If you yourself are found to be a carrier of a genetic mutation, then testing your partner would be important to determine if they are a carrier of the same disease as well.
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Impactful Quote of the Week
"Medicine is a science of uncertainty and an art of probability."
- Sir William Osler
All my best,
Brian Hoeflinger
P.S. - if you enjoyed this newsletter, you may enjoy my book that details my life as neurosurgeon and the loss of my oldest son, Brian (see below a synopsis).
My Book
Life and Death . . . Two words with such opposite meaning and which inflict such contradictory emotions and yet are so closely intertwined in our lives. As parents, we bring meaning and life into this world through our children. Our lives become defined as a result. We learn the joy, hardship, and responsibility of shaping an innocent life. But a day will come when that life will be taken. For some, death will come too soon. This is the story of my son, Brian Nicholas Hoeflinger, who died unexpectedly at age 18.
https://doctorhoeflinger.com/products/the-night-he-died-the-harsh-reality-of-teenage-drinking
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Medical Trivia Answer:
The correct answer is A) Mitochondria
