There are over 6,500 genetic conditions, affecting an estimated 300 million people worldwide. Genetic testing can reveal if you have one of these conditions or it can help determine your likelihood of developing or passing one on. If you are having fertility issues, genetic testing can also tell you if a genetic condition is hindering your chances of conceiving. Genetic testing during pregnancy can also determine if your child already has a genetic condition.
Learn more about how genetic conditions arise, the difference between inherited diseases and random mutations, and how genetic testing can help make the journey to parenthood easier to navigate.
Key takeaways
- Genetic testing before or during pregnancy can reveal whether you have a genetic condition, or if you are a carrier of a gene mutation.
- Some genetic conditions are inherited, while others occur randomly before birth.
- Genetic susceptibility means a person has an increased likelihood of developing a particular illness based on their genetic makeup.
- Some genetic conditions, like cystic fibrosis and Klinefelter syndrome, may cause male-factor infertility.
How do genetic conditions arise?
You receive half of your genes from each biological parent, as the egg and sperm each carry their own set of chromosomes. When you receive an altered gene from one of your parents, you are at risk of developing a particular condition. But not all genetic conditions are passed down from your parents. Some gene mutations occur randomly before birth, in which case a child may have a genetic disorder that neither of the parents carries. And other gene mutations can occur over a person’s lifetime due to environmental exposure. Genetic testing can help uncover the likelihood of developing illnesses based on genetic makeup.
Examples of inherited genetic conditions
Some inherited genetic conditions include cystic fibrosis, fragile X, and Tay-Sachs disease, which can all be detected by genetic testing before birth. Parents undergoing genetic testing can see if they are carriers and assess the likelihood of their child inheriting the condition, or genetic testing can be done on a fetus while in utero.
Here’s what you should know about these inherited genetic conditions:
- Cystic fibrosis: There are an estimated 40,000 children and adults living with cystic fibrosis in the U.S. In people with cystic fibrosis, there is a mutation in the transmembrane conductance regulator (CFTR), causing mucus to build up and damage organs in the body. If both parents are carriers of the non-functioning cystic fibrosis gene, there is a one-in-four chance that both will pass on the gene to their child.
- Fragile X: Research suggests that fragile X affects an estimated 1 in 7,000 males and 1 in 11,000 females. This rare inherited condition is caused by changes in a gene called Fragile X Messenger Ribonucleoprotein, which creates a protein crucial to brain development. The gene for Fragile X is carried on the X chromosome, which means either parent can pass on the mutated gene to their children.
- Tay-Sachs disease: While anyone can be affected by Tay-Sachs disease, it is most common among people with Ashkenazi Jewish ancestry. Approximately 1 in every 27 Jewish people in the U.S. is a carrier of the Tay-Sachs disease gene. Tay-Sachs disease is caused by a defective gene on chromosome 15 and stops the nerves from working properly. It can only be inherited if both parents have this gene mutation.
Examples of spontaneous genetic conditions
Spontaneous genetic conditions occur randomly and are not inherited from parents. Some examples include Klinefelter syndrome and Turner syndrome. These conditions are typically diagnosed during puberty based on symptoms and genetic testing like karyotyping, which examines the chromosomes of the child. They can also be detected before birth through an amniocentesis, which assesses the amniotic fluid for evidence of genetic abnormalities, and is yet another example where genetic testing can play a crucial role during pregnancy.
Here’s what you should know about these spontaneous genetic conditions:
- Klinefelter syndrome: Klinefelter syndrome is a chromosomal condition in which a biological male is born with an additional copy of an X chromosome. This genetic condition occurs randomly during the division of the sex chromosomes in the egg or sperm, typically causing testicular failure leading to androgen deficiency. It is estimated that the condition affects approximately 1 in 500–1,000 males.
- Turner syndrome: Turner syndrome is a genetic condition that results when one of the X chromosomes is missing or partially missing. It affects more than 70,000 biological females in the U.S. and causes a variety of medical and developmental problems, including short height, failure of the ovaries to develop, and heart defects.
Examples of genetic susceptibility to illness
In some cases, a person has an increased likelihood of developing a particular illness based on their genetic makeup. This is called genetic predisposition, or susceptibility, and results from specific genetic variations that are often inherited from a parent. These genetic mutations contribute to the development of a disease but they do not directly cause it. Some individuals with a predisposing genetic variation will never get the disease, even if their relatives have it.
Genetic variations in the BRCA1 or BRCA2 genes mean that a person has a genetic predisposition to breast and ovarian cancer. This means their risk of developing these diseases is higher than those without the variation but it can also depend on other factors like lifestyle choices and environmental exposure. Genetic testing can help detect the likelihood of these diseases developing.
How are genetic conditions inherited by offspring?
You can pass on a genetic condition to your offspring in a number of ways. Some require just one parent to be a carrier, while some require both. This is why genetic testing is particularly important before or during pregnancy.
Types of inheritance:
- Autosomal dominant: An autosomal dominant disorder requires a single copy of a mutated gene (from one parent). Mutations to BRCA1 and BRCA2 genes are transmitted this way.
- Autosomal recessive: An autosomal recessive disorder requires two copies of the mutated gene (one from each parent) to cause the disorder. Cystic fibrosis and Tay-Sachs are autosomal recessive genetic conditions.
- X-linked dominant: X-linked dominant disorders are caused by variants in genes on the X chromosome. A mutation in one copy of an X-linked gene will result in disease for both males and females. Fragile X is an example of an X-linked dominant genetic condition.
- X-linked recessive: X-linked recessive disorders are also caused by variants in genes on the X chromosome but a biological female will need two copies to be affected. Only one mutation is needed for males because they only have one X chromosome. Fathers cannot pass X-linked mutations on to their sons. Examples of X-linked recessive diseases are hemophilia and Fabry disease.
- Y-linked: Y-linked disorders are caused by variants in genes on the Y chromosome. Because only males have a Y chromosome, in Y-linked inheritance, a variant can only be passed from father to son. The mutation may cause characteristics like webbed toes or Y-chromosome microdeletions, which can lead to conditions such as oligospermia, azoospermia, and teratospermia.
- Codominant: In codominant inheritance, two versions (alleles) of the same gene are expressed and each version makes a slightly different protein. Having the AB blood type is an example of a codominant inheritance.
- Mitochondrial: In this type of inheritance, the mitochondria contain their own DNA. Also known as maternal inheritance, mitochondrial mutations are exclusively inherited from mothers. An example of a mitochondrial disorder is Leber hereditary optic neuropathy, a form of inherited vision loss.
What is genetic testing?
Genetic testing is a type of medical assessment that detects changes in genes, chromosomes, or proteins. It can be performed with a sample of blood, hair, skin, amniotic fluid, saliva, or other tissue. A person considers genetic testing to confirm or rule out a suspected genetic condition or it can help determine their likelihood of developing or passing on a genetic disorder.
A genetic test may examine the DNA inside cells to identify mutations that may be associated with a disease. Or it can analyze whole chromosomes or long lengths of DNA to check for large genetic changes, such as an extra copy of a chromosome, that may cause a genetic condition. A karyotype is a type of genetic testing that looks at chromosomes. Genetic testing may also study the amount or activity of proteins or enzymes to detect abnormalities related to a disorder.
Different types of genetic tests include:
- Carrier testing: This type of genetic testing can reveal whether you carry a gene for certain genetic disorders. It is ideal for those who have a family history of a genetic disorder and for people in certain ethnic groups with an increased risk of genetic conditions. If planning a family, genetic testing carried out on both parents can provide information about a couple’s risk of having a child with a genetic condition.
- Diagnostic testing: Diagnostic testing is used to identify or rule out a specific genetic condition. This type of genetic testing is ideal for those who are having symptoms of a particular condition. It can also be performed before birth.
- Newborn screening: This type of test is used to identify genetic diseases that can be treated early. The U.S. Health Resources and Services Administration recommends newborn screenings for a set of 35 conditions.
- Prenatal screening: Prenatal genetic testing checks for abnormalities in a fetus’s genes before birth. Doctors will typically recommend this type of test during pregnancy if there is an increased risk of a genetic condition.
Benefits of genetic testing
Genetic testing empowers people to make informed decisions about their health. If you receive a positive result, you can start scheduling recommended check-ups or screenings to prevent, monitor, or even treat a genetic disease. Finding out you are a carrier of a gene mutation may impact your decision on having children. Genetic testing on a fetus in utero can also identify spontaneous genetic disorders early in life so you can develop a suitable treatment plan.
Genetic testing costs
The cost of genetic testing ranges from under $100 to more than $2,000, depending on the type of test. Most tests are covered by insurance, especially if the pregnancy is considered high risk. Gathering information about your family history is a good first step in getting coverage for these types of tests, making genetic testing a crucial feature of any pregnancy.
Genetic disorders that cause male-factor infertility
It is estimated that 10–15% of male-factor infertility cases are due to genetic disorders. These disorders may affect how much sperm is produced or how the sperm is transported in the body.
These disorders include:
- Cystic fibrosis: Research shows that 97–98% of men with cystic fibrosis are infertile because of abnormal development of the vas deferens. Males with this disorder may still produce healthy sperm, but they cannot transfer this sperm to the semen. Using assisted reproductive technology like testicular sperm extraction (TESE), paired with in vitro fertilization (IVF), can be a successful intervention.
- Y-chromosome microdeletions: Unlike cystic fibrosis, Y-chromosome microdeletions do affect sperm production. Those with this genetic disorder may struggle with low sperm count, azoospermia, and a high percentage of abnormal sperm.
- Klinefelter syndrome: Klinefelter syndrome also causes male-factor infertility due to azoospermia and low testosterone levels. Males with this condition can still father a child as sperm is found in more than 50% of cases. Like cystic fibrosis, using assisted reproductive technology, like TESE, can help.
- Kallmann syndrome: Commonly detected during adolescence, Kallmann syndrome causes a lack of hormones that regulate sexual development. Most males with this condition are infertile because they cannot produce sperm, though sperm production may be induced by long-term hormone therapy.
Genetic testing for infertility
Genetic testing may be recommended by your doctor based on results of a semen analysis. If you are having difficulty conceiving and your semen analysis has indicated low sperm count or low sperm quality, a genetic test can determine if a specific genetic condition is the reason.
But you don’t have to wait until you are trying to conceive to have your sperm tested. Getting insights about your sperm health can help you devise an action plan early to make the family-building process easier down the line. Testing your sperm and uncovering a genetic condition can also provide a window into your overall health so you can work on prevention or treatment.
Order an at-home sperm testing kit from Legacy to get started.