Genetic Mutation
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Medically reviewed by Soma Mandal, MD
Genes are the inherited material you get from both your parents that are made from strands of molecules called DNA. Long stretches of DNA are packed with other materials, like proteins, to make 46 chromosomes. Genes contain the information, or "code", needed so your body can make the many proteins it needs to function. A genetic mutation is an alteration in the genetic code found in DNA.
A mutation changes the specific instructions of the gene, coded through small components of DNA. Because a genetic mutation changes the genetic coding, the resulting protein might not work the way it was initially supposed to, which can lead to disease.
Some mutations are present from birth. You can inherit some gene mutations that first occurred in one of your parents, grandparents, or an older ancestor. Other genetic mutations happen as a natural part of aging, and some happen after exposure to substances that cause damage to your DNA.
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Types
The types of genetic mutations are complicated because scientists conceptualize genetic mutations in different ways. They can be classified by the type of molecular genetic change, whether they're inherited vs. acquired, or if they're dominant vs. recessive.
Type of Molecular Genetic Change
Some mutations change just one tiny part of the genetic code, making it “incorrect." This might lead to a change in the effectiveness of the protein for which it codes. The protein might have missing parts, a part that doesn’t work as well, a part in the wrong place, or it might not be made at all.
Other types of mutations affect longer stretches of DNA and even more than one gene. For example, part of one gene might connect to the wrong part of the DNA sequence. This sometimes causes an abnormal combined protein to form. This kind of change can happen in some cancers.
In some cases, large stretches of DNA are affected, and the mutation impacts multiple genes. Many genes might be completely absent, or there might be an extra copy of a long stretch of genes. One example is Down syndrome, in which the person has an extra copy of the genes found in chromosome 21.
Not all mutations make a difference. Some "silent" mutations don’t change how the protein functions, so they don’t cause any problems.
Inherited vs. Acquired Mutations
You might inherit a mutated gene from one or both of your parents, meaning your parents had the mutation in their DNA and it became part of your DNA. In that case, you’d have the gene mutation in all your cells from conception.
This might be important if the mutation directly causes a disease or greatly increases your risk of disease. A mutation like this might be passed down from generation to generation. The actual event that changed the DNA might have happened a very long time ago.
In contrast, an acquired mutation occurs at some point later in life. It affects some of your cells, not all the cells in your body. It’s normal to acquire new mutations as part of aging, and most of them don’t make a difference. However, some acquired mutations can lead to cancer or other medical conditions. Scientists are still finding different types of gene mutations and determining how they are connected to certain diseases.
Some related terminology is “germline” versus “somatic” mutation. A mutation in the germline affects the genes in the cells that one’s children receive, so it can be transmitted across generations. However, mutations in other types of cells in the body, called “somatic cells,” can’t affect future generations.
Dominant vs. Recessive Gene Mutations
For some gene mutations that can cause disease, it matters whether you get a copy from just one or from both of your parents. Some diseases require you to have gene mutations from both of your parents in order for the disease to develop. Anyone can have a single gene mutation that doesn't cause illness; this is known as being a "carrier."
For dominant gene mutations, having only one copy of the abnormal mutation can give you the disease. You can inherit it from either of your parent's DNA. For recessive gene mutations, you need to get copies of the mutation from both sides of your family to get the disease.
Inheritance is also more complicated for mutations on the sex chromosomes (e.g., the “X” or "Y" chromosome). Depending on one’s biological sex, you might need to inherit a gene from just one or from both parents to get the associated disease.
Causes
You get inherited mutations from your parents. Even though the actual mutation occurred in your family's DNA long ago, scientists still refer to them as “mutations” if they result in certain diseases.
Acquired mutations are caused by more recent changes to the DNA during one’s lifetime. Getting some acquired mutations is a normal part of aging, but exposure to substances that can alter your DNA can increase your risk of getting more of them.
Substances that increase the risk of such mutations can increase your risk of cancer. Examples include tobacco products, ultraviolet radiation from the sun, X-rays from medical imaging, radioactive substances (like radon), and many different chemicals.
How Do Genetic Mutations Affect the Body?
Scientists think that people inherit roughly 50,000 different genes, half from each parent. A genetic mutation can occur in any of these genes. The impact of a mutation varies widely based on the type of protein it affects and what that protein normally does.
A mutation might affect your muscles, heart, digestive system, brain, blood, or any other body part. Because some proteins are expressed in more than one system, some mutations affect multiple areas.
Some mutations are so severe that the fetus does not survive until birth. In cases of spontaneous miscarriage, at least half of fetuses carry a genetic mutation. These are typically severe chromosomal mutations involving many genes.
Genetic Diseases vs. Multifactorial Diseases
Some genetic mutations directly cause disease. For these kinds of diseases, sometimes called “genetic diseases,” you need to inherit one (dominant) or two (recessive) copies of the abnormal mutation to get the disease.
However, many diseases are multifactorial, meaning they have both genetic and environmental components causing them. Having variations of certain genes (i.e., having certain gene mutations) can increase your risk of a disease, but a lot more is involved.
For example, having a certain gene mutation might slightly increase your risk of getting Alzheimer’s disease. However, you wouldn’t necessarily get Alzheimer’s disease if you have this mutation, and some people without the mutation also get the disease.
Harmful, Neutral, and Beneficial Mutations
Most new mutations are neutral or harmful. However, some gene mutations cause advantageous protein changes. If so, that genetic mutation may eventually become widespread in the population. Mutations are a part of how species adapt to the environment over very long periods of time through the process of evolution.
Genetic Disorders in Humans
Thousands of different genetic disorders can affect human beings. Although they range from somewhat uncommon to exceedingly rare, together they affect around 1 in 12 people.
Genetic diseases caused by inherited abnormal mutations include:
Sickle cell disease (SCD): SCD causes a person’s hemoglobin (a protein in red blood cells) not to form correctly, causing their red blood cells to form a “sickle” shape. It can cause anemia, repeated pain crises, and organ damage.
Inherited thrombophilia: Sometimes called hereditary thrombophilia, this greatly increases your risk of abnormal blood clots that can affect the legs, lungs, or other parts of the body. A mutation in the prothrombin gene is a common cause of this condition.
Hemophilia: This can cause frequent and severe bleeding. It is caused by mutations in genes such as FVIII which help make clotting factors to stop your body from bleeding.
Familial hypercholesterolemia: Results from a genetic mutation can lead to very high levels of LDL-type cholesterol and can lead to heart attacks at a very young age.
Cystic fibrosis (CF): CF is caused by mutations in the CFTR gene, which makes a protein responsible for the regulation of the chloride ion in cells. It leads to thick mucus build-up in the body, affecting the lungs, digestive tract, and other organs.
Huntington’s disease: Caused by mutations in the HD gene, this disease causes the nerves in the brain to break down. This can lead to involuntary movements and cognitive decline, among other symptoms.
Duchenne muscular dystrophy: This condition generally affects males. It's caused by mutations in the DMD gene on the X chromosome and causes progressive muscle and skeletal weakness.
Tay Sachs disease: This causes a build-up of fatty acids in the brain that progressively destroys cells in the nervous system. It results from a mutation on chromosome 15.
Autosomal dominant polycystic kidney disease (ADPKD): Caused by mutations in the PKD1 or PKD2 gene, it causes abnormal cysts in the kidneys, which can cause kidney failure.
Fragile X syndrome: This results from abnormalities in the FMR1 gene, leading to mental disability and other symptoms.
Down syndrome: This causes mental disability and an increased risk of heart defects and digestive problems due to mutations leading to extra genes from chromosome 21.
Cancer
Acquired genetic mutations are part of what causes cancer. However, inheriting certain genes can increase your risk of developing these acquired mutations and, in turn, getting cancer. This is sometimes just a small increased risk, but the risk can be greater with some genes.
For example, "BRCA" proteins are involved in DNA repair. Having a mutation in the BRCA1 or BRCA2 genes dramatically increases your risk of breast, ovarian, and some other cancers, and it increases your risk of getting these cancers at a younger age. Therefore, it sometimes makes sense to test for these mutations as part of preventive medical care, especially if you have a family member (such as your mother, aunt, or grandmother) who had breast or ovarian cancer.
These tests are not part of routine preventative medical care. Individuals are selectively screened for risks and then tested based on their personal and family history.
Genetic Testing
Genetic counseling is a good idea if you've been diagnosed with a genetic disease, have a known genetic disease in your family, or if you're displaying symptoms of a genetic disease.
A specialist in genetics can talk to you about your risks of a certain condition in your specific medical context. Genetic testing is often needed to get a clear picture.
To perform genetic testing, your healthcare provider will collect your DNA by swabbing your cheek or taking a sample of blood or saliva. Then your DNA will be examined in a laboratory to see if you have specific disease-causing mutations.
Treatments for Genetic Mutations and Resulting Diseases
Treatment for genetic mutations varies a great deal based on the mutation and the specific disease it causes. For example, treatment for muscular dystrophy varies quite a bit from treatment for a genetic problem that abnormally increases your cholesterol levels.
Historically, healthcare providers haven’t been able to directly treat the mutation itself. Instead, they focused on reducing symptoms and improving your day-to-day function. Depending on the situation, this might involve medications, changes in diet, and exercise, among other treatments and lifestyle factors. For acquired mutations leading to cancer, the focus is mostly on removing the unhealthy cells (e.g., through surgery, chemotherapy, or radiation).
Newer technologies are making it possible to treat some genetic conditions at a deeper level. In a stem cell transplant, the approach is to wipe out your unhealthy blood-forming stem cells (containing the mutation). Then, you receive a stem donation from someone without the mutation, which eliminates disease symptoms. However, this isn't possible for all genetic conditions.
Researchers have also developed gene therapies. These work by replacing or deactivating disease-causing mutations. This is a newer treatment area with potential risks, but it may eventually provide radically improved management for various genetic diseases, such as cystic fibrosis, hemophilia, and sickle cell disease.
Preventing a Mutation
Although you can’t always prevent getting a potentially harmful mutation or passing one on to your children, you may be able to reduce your risks.
Preventing New Genetic Mutations in Yourself
You can take steps to reduce your risk of getting potentially harmful mutations, including the following:
Avoid tobacco products, all of which increase your risk of cancer and other disease
Protect your skin from radiation from the sun by limiting exposure during the middle of the day and using sunscreen and coverups
Eat a high-fiber diet with lots of fruits and vegetables
Only get medical tests using radiation when truly needed, such as X-rays and especially CT scans
Limit your consumption of alcohol
Preventing Passing Down a Harmful Genetic Mutation
In some diseases, parents can pass the disease to their children even if they don’t have symptoms themselves. Genetic tests can show if you have a certain mutation that might cause disease in your child, so consult with an expert such as a genetic counselor.
People who are carriers of disease-causing mutations have some options. For example, some people can use genetic testing paired with in vitro fertilization (IVF) to make sure their child won’t have the disease mutation. You can also use genetic testing during pregnancy to see if a developing fetus carries specific gene mutations.
A Quick Review
Gene mutations can impact your health significantly. Depending on where they occur and their type, mutations can cause a broad range of disorders and diseases. When mutations occur in genes responsible for making important proteins, they can disrupt normal cell functions.
Genetic mutations are classified in different ways, including the type of molecular genetic change, if they're inherited or acquired, or if they're dominant or recessive. Some genetic mutations directly cause disease while some require both genetic and environmental components in order to mutate.
It is possible to develop thousands of genetic disorders, each very different from the last. You may be able to reduce your risk of developing a genetic disorder through some modifiable lifestyle factors. Genetic testing can also help your healthcare providers determine if you have certain gene mutations, if you're a carrier, or if your child is at risk of inheriting a mutation.
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