Yes, genes can be changed, both deliberately through medical technology and naturally through environmental influences on your body. The ways this happens range from precise surgical edits to your DNA code using tools like CRISPR, to subtler chemical modifications that turn genes on or off without altering the underlying sequence. These aren’t hypothetical possibilities: over 30 gene therapies are already approved by the FDA, and your own lifestyle is reshaping your gene activity right now.
Two Ways Genes “Change”
It helps to separate two very different things people mean when they ask whether genes can be changed. The first is a permanent alteration to the DNA sequence itself, like fixing a typo in a genetic instruction manual. The second is a change in how actively a gene is read and used by your cells, without touching the sequence at all. Both are real, and both have significant effects on health.
Changing the actual DNA sequence requires either a natural mutation (from radiation, chemicals, or copying errors during cell division) or a deliberate intervention using gene-editing technology. Changing gene activity, on the other hand, happens constantly throughout your life in response to diet, exercise, stress, and chemical exposures. Scientists call this second category epigenetics.
How Gene Editing Works
The most widely known gene-editing tool is CRISPR-Cas9, which works in three basic steps: recognition, cleavage, and repair. A guide molecule directs the Cas9 protein to a specific spot on your DNA. The protein then cuts both strands of the DNA double helix at that precise location. Your cell’s own repair machinery kicks in to stitch the break back together, and scientists can exploit that repair process to delete a faulty gene, correct a single-letter error, or insert new genetic material.
The cell has two main ways to fix a double-strand break. One is a quick, somewhat messy process that simply glues the cut ends together, sometimes introducing small insertions or deletions that disable the gene. The other uses a template, like a correct copy of the gene, to make a clean repair. Researchers choose which approach to harness depending on whether they want to knock out a harmful gene or replace it with a working version.
Newer, More Precise Tools
Standard CRISPR cuts both strands of DNA, which is effective but carries risks. Newer approaches avoid that double-strand break entirely. Base editing, for example, chemically converts one DNA letter into another at a targeted location without cutting the helix. There are two main types: one converts C-G pairs to T-A pairs, and the other converts A-T pairs to G-C pairs. Together, they can make all four possible single-letter swaps.
Prime editing goes further still, capable of making any of the twelve possible letter-to-letter changes plus small insertions and deletions, all without breaking both DNA strands. Think of base editing as a pencil eraser that swaps one letter, and prime editing as a word processor that can rewrite a short phrase.
How Genes Change Without Editing
Your DNA sequence is essentially the same in every cell of your body, yet a liver cell behaves nothing like a brain cell. The difference comes down to which genes are active and which are silent, and that activity level shifts throughout your life based on chemical tags attached to your DNA and the proteins that package it.
The most studied of these tags is DNA methylation: the attachment of a small chemical group to specific points along the DNA strand. About 70% of gene promoter regions (the “on switches” for genes) sit within stretches of DNA prone to this kind of tagging. When these regions get heavily methylated, the gene effectively shuts off. The DNA physically tightens around its packaging proteins, blocking the cellular machinery that would normally read it.
The packaging proteins themselves, called histones, can also be chemically modified. Adding certain chemical groups loosens the DNA-histone grip, opening things up so a gene can be read. Other modifications tighten the grip and silence the gene. Your cells are constantly adjusting these settings in response to signals from your environment.
Lifestyle Directly Shapes Gene Activity
A large population study from Germany examined how diet, physical activity, smoking, and alcohol intake affect DNA methylation patterns in over 4,100 people. All four lifestyle factors contributed to measurable differences in methylation across the genome, and the strongest effects came when all four factors were considered together. These weren’t small, obscure changes: they affected pathways involved in nerve signaling and cellular communication, and they influenced “methylation age,” a biological clock that reflects how quickly your cells are aging at the molecular level.
Smoking provides one of the clearest examples. It reduces methylation at a specific gene involved in blood clotting and inflammation, an effect that has been confirmed in both blood and fat tissue. The important takeaway is that your daily habits are not just affecting your health in vague, general ways. They are physically rewriting the chemical annotations on your DNA, turning genes up or down in patterns that can persist for years.
Gene Therapy in Medicine Today
Gene editing and gene therapy have moved well beyond the laboratory. The FDA has approved more than 30 cellular and gene therapy products, targeting conditions from blood cancers to inherited blindness to hemophilia. One approved therapy restores vision in people with a specific form of inherited retinal disease. Several others reprogram a patient’s own immune cells to hunt down cancer.
To get new genetic material into cells, most therapies use modified viruses as delivery vehicles. The virus’s own disease-causing genes are stripped out and replaced with therapeutic ones. Adeno-associated viruses (AAV) are among the most commonly used carriers because they rarely integrate into the patient’s chromosomes, instead persisting as separate elements inside the cell. Different AAV types naturally home to different tissues (muscle, retina, liver, heart), giving researchers some control over where the therapy ends up.
Sickle Cell: A Landmark Case
One of the most striking examples is Casgevy, the first CRISPR-based gene therapy approved by the FDA, for sickle cell disease. Rather than fixing the mutation that causes sickle-shaped red blood cells directly, Casgevy takes a clever indirect route. It edits a gene called BCL11A in a patient’s blood-forming stem cells. BCL11A normally suppresses production of fetal hemoglobin, a version of the oxygen-carrying protein that humans naturally make before birth and then gradually stop producing. By dialing down BCL11A, the therapy reactivates fetal hemoglobin production. Fetal hemoglobin doesn’t sickle the way the mutant adult form does, so patients experience significantly fewer painful blockages in their blood vessels and can stop needing regular transfusions.
Risks and Limitations
The biggest technical concern with CRISPR-style editing is off-target effects: the editing tool cutting DNA at the wrong location. When the Cas9 protein encounters a stretch of DNA that closely resembles its intended target, it can make unintended cuts. These stray edits might land in harmless stretches of DNA, but they could also disrupt important genes, potentially causing problems ranging from cell death to, in a worst-case scenario, cancer-promoting mutations.
Beyond single-letter errors, double-strand breaks can occasionally trigger larger problems: big deletions of DNA segments, rearrangements of chromosomal material, or pieces of one chromosome fusing with another. These events are harder to detect than small off-target cuts and remain an active area of concern. The newer editing approaches (base editing and prime editing) were developed in part to avoid these risks by eliminating the need for a full double-strand break.
Somatic vs. Germline Changes
Every gene therapy currently approved targets somatic cells, the ordinary cells of your body. Changes to somatic cells affect only the treated person and cannot be passed to children. Germline editing, which would modify eggs, sperm, or embryos, is a fundamentally different proposition because those changes would be inherited by every future generation. Germline editing in humans remains largely off-limits in most countries due to ethical concerns and scientific uncertainty about long-term consequences.
The Cost of Changing Genes
Gene therapies are among the most expensive medical treatments ever developed. The priciest therapy on the U.S. market, Lenmeldy (for a rare neurological disorder), costs $4.25 million per dose. Several others exceed $3 million, including Hemgenix for hemophilia B at $3.5 million, Elevidys for Duchenne muscular dystrophy at $3.2 million, and Lyfgenia for sickle cell disease at $3.1 million. Zolgensma, a gene therapy for spinal muscular atrophy in young children, costs $2.32 million.
These prices reflect the complexity of manufacturing a personalized biological product, often from a patient’s own cells, and the small number of patients eligible for each therapy. Many insurers do cover these treatments, sometimes through installment-based payment models, because a one-time gene therapy can replace decades of ongoing treatment costs. Still, access remains uneven, particularly outside wealthy countries.