In my last post, I talked all about what is means when you are a genetic carrier of a recessive gene. To recap, the recessive gene will not cause disease, but your partner also has that recessive gene, you may have a child with a disease. Let’s think about the options, using a capital letter (G) as the normal gene and a lower case letter (g) as the recessive mutated gene.
If you are a carrier, you’re have one copy of G and one copy of g (or Gg). What if you have a child with someone who isn’t a carrier (GG)? If you look at the possibilities (to the left) you have a 50/50 chance of having a child who isn’t a carrier or one who is. But you will not have a child who has the disease. On the other hand, if both you and your partner are carriers (see the picture on the right), you have 25% chance of having a child who isn’t a carrier, 50% chance of having a child who’s a carrier, and 25% chance of having a child who has the disease.
If you’re a carrier and your partner is a carrier, you know your odds. So what are your options? Before I start, if you’re dealing with this personally, please discuss all of this with a trained medical professional. I can explain the biology of why things happen, but only your doctor can give you medical advice and treatment options. Also, these decisions are all personal to you. There is no one answer, and what works for you may not work for someone else – and this is often what we face when making these very personal medical decisions.
- If you know that you and your partner are both carriers for a particular disease, you can choose not to get pregnant and avoid the risk altogether
- Alternatively, you can get pregnant and monitor the pregnancy closely. Go ahead and roll the dice! There is a 25% chance of having a child with that disease and a 75% chance that they won’t. Having the knowledge in advance, you will know the likelihood and can monitor the pregnancy accordingly
- There are tests like chorionic villus sampling (CVS) that can test for genetic diseases (such as Tay-Sachs disease) before birth, if both you and your partner are carriers for a recessive gene that causes disease
- If the developing child is found to have a genetic disease, depending on the disease and severity (e.g., if they will or will not survive at birth), there is the option to terminate the pregnancy. There also may be options for treatments while the child is developing or immediately at birth that may help decrease the severity of the disease right away.
- You can choose instead to use a sperm or egg donor from someone who doesn’t carry that recessive gene.
- You can use in vitro fertilization and check the genes of the embryo pre-implantation to select those that do not have two copies of the recessive genes.
- Choose to adopt
As an aside, I asked my primary care physician about carrier testing a few years ago. Without a family history of any genetic diseases, she was resistant (if not downright hostile) about me wanting to get carrier testing, and mentioned that insurance likely wouldn’t pay for the testing. I’m hoping that my experience was not the norm, however, I don’t think that most primary care physicians have a deep understanding of genetics and genetics diseases and may be uncomfortable suggesting this type of screening because they would not know how to best interpret the results. Interestingly, a number of companies now exist that will perform the carrier testing for you for a nominal fee, such as Pathway Genomics, Counsyl, and Natera. I cannot recommend or discourage you from using or not using these services, however you generally need to work with your doctor to order these tests.
Again, these are all options, not medical advice, and all up to you as to what works best for you and your partner. But with the knowledge of what may happen and why it may happen, you are at least armed with information to ask meaningful questions about yours and your non-existent child’s potential genes before or during your pregnancy,