DNA can be changed in two fundamentally different ways: editing the genetic code itself using laboratory tools like CRISPR, or altering how genes behave through lifestyle and environmental factors without touching the underlying sequence. The first approach is cutting-edge medicine used to treat serious genetic diseases. The second happens naturally in your body every day in response to what you eat, drink, and experience.
Gene Editing vs. Gene Expression
Your DNA is both a fixed code and a flexible system. The sequence of letters (A, T, C, G) that makes up your genome is set at conception, but your body constantly adjusts which genes are turned on or off. These adjustments, called epigenetic changes, respond to your environment and habits. Gene editing, by contrast, physically rewrites the DNA sequence itself, permanently altering the instructions your cells follow.
Both matter, but they operate on completely different scales. Epigenetic changes happen to everyone, all the time, and many are reversible. Direct DNA editing requires specialized molecular tools, is currently limited to medical treatments, and in most cases is irreversible. Understanding both gives you the full picture of how DNA can be “changed.”
How CRISPR Edits DNA
CRISPR-Cas9 is the most widely known gene-editing tool. It works like a molecular search-and-replace function. A short piece of guide RNA is designed to match a specific DNA sequence in the genome. When it finds that sequence, the Cas9 protein acts as molecular scissors, cutting both strands of the DNA double helix at that precise location.
Once the DNA is cut, the cell rushes to repair the break using one of two natural pathways. The faster, messier option is called non-homologous end joining (NHEJ), where the cell essentially glues the broken ends back together. This process is error-prone and often introduces small insertions or deletions at the cut site, which can disable a gene. That’s useful when the goal is to knock out a harmful gene.
The more precise option is homology-directed repair (HDR), where the cell uses a provided DNA template to fill in the gap with an exact replacement sequence. This is how scientists can swap a disease-causing mutation for a healthy version. The catch: HDR is significantly less efficient than NHEJ, meaning a large fraction of edited cells end up with random insertions or deletions rather than the clean replacement researchers intended.
Newer, More Precise Editing Tools
Traditional CRISPR’s reliance on cutting both DNA strands creates risks. Newer approaches avoid this entirely. Base editing chemically converts one DNA letter into another without making a full cut. Instead of scissors, think of it as a pencil eraser that changes a single character. Adenine base editors, which convert A-to-G, are remarkably clean, producing the correct edit with 99.9% purity and virtually no unintended insertions or deletions.
Prime editing goes further. It uses a modified Cas9 that nicks only one DNA strand instead of both, paired with a reverse transcriptase enzyme that writes new genetic information directly into the genome. This allows not just single-letter swaps but also small insertions and deletions at a precise location, all without the double-strand break that makes traditional CRISPR risky. Both base editing and prime editing represent a significant leap in precision, though they’re still newer and less tested in clinical settings.
Getting Editing Tools Into Cells
Building a gene editor is only half the challenge. The other half is delivering it to the right cells inside a living person. Two main strategies exist: viral vectors and lipid nanoparticles.
Viral vectors use modified, harmless viruses as delivery vehicles. Because viruses naturally evolved to inject genetic material into cells, they’re highly efficient at getting editing tools where they need to go. The trade-off is that they can trigger immune responses and are harder to manufacture at scale.
Lipid nanoparticles, tiny fat-based capsules, offer a safer alternative. They can carry genetic material ranging from small RNA molecules to much larger DNA sequences, and they can be engineered with surface molecules that direct them to specific cell types like liver or tumor cells. Their delivery efficiency is still lower than viral vectors, but they avoid many of the immune-related complications. The COVID-19 mRNA vaccines used this same lipid nanoparticle technology, which accelerated research into their use for gene therapy.
What Gene Editing Treats Today
Gene editing has moved from the lab into real medical treatments. Casgevy, approved for sickle cell disease and transfusion-dependent beta-thalassemia, is the first CRISPR-based therapy available to patients. It works on somatic cells, meaning the edits affect only the treated individual and are not passed to future children. Clinical trials for other conditions, including certain cancers and inherited blood disorders, are underway.
Somatic editing (changing DNA in body cells) is fundamentally different from germline editing (changing DNA in eggs, sperm, or embryos). Somatic edits die with you. Germline edits would be inherited by every future generation. For this reason, germline editing in humans is effectively banned or heavily restricted in most countries, including the United States, Europe, Australia, Japan, and China. Even somatic therapies delivered inside the body carry a small theoretical risk of accidentally modifying reproductive cells, so clinical trials must demonstrate this risk is minimized.
Risks of Direct DNA Editing
The most significant concern with CRISPR is off-target effects: unintended edits at the wrong locations in the genome. These stray cuts can disrupt genes that weren’t supposed to be touched, potentially affecting cell function or gene regulation in unpredictable ways. Research in zebrafish found that 26% of offspring from edited founders carried an off-target mutation, and 9% had large structural rearrangements in their DNA. While animal models don’t translate directly to human therapy, these numbers illustrate why rigorous pre-testing with patient tissue samples is considered essential before clinical use.
Even at the intended target site, CRISPR can cause larger disruptions than expected. Studies have documented large structural variations, chromosomal rearrangements, and unintended changes to the chemical tags that control gene activity at cut sites. These effects are a major reason newer tools like base editing and prime editing, which avoid double-strand breaks, are attracting intense interest.
How Lifestyle Changes Gene Expression
You don’t need a laboratory to change how your DNA behaves. Your body constantly adds and removes chemical tags on DNA and the proteins that package it, turning genes up or down in response to environmental signals. This is epigenetics, and it’s influenced by ordinary daily choices.
Diet is one of the most studied factors. Diets high in polyunsaturated fatty acids can generate oxidative stress, which has been directly linked to epigenetic alterations. In cell studies, arachidonic acid (found in meat and eggs) changed methylation patterns on genes involved in blood vessel growth. Nutrients like folate, B12, and other methyl donors play a direct role in supplying the chemical groups your body uses to tag DNA.
Alcohol exposure has clear epigenetic effects. In animal studies, chronic alcohol exposure altered methylation on genes involved in memory and learning. Acute alcohol exposure changed the methylation of cell cycle genes, slowing cell growth. During pregnancy, alcohol exposure altered DNA methylation patterns in embryos in ways linked to neural tube defects and abnormal development. Environmental toxins also leave epigenetic marks. People exposed to high levels of arsenic showed significant increases in methylation on tumor-suppressing genes p53 and p16, effectively silencing protective genes.
The key distinction: these changes affect which genes are active, not the DNA sequence itself. Many epigenetic changes are reversible. Improving your diet, reducing alcohol intake, or removing toxic exposures can shift methylation patterns back. This is why epigenetics is sometimes described as the bridge between nature and nurture.
Cost and Access Barriers
Even where gene-editing therapies exist, access is extremely limited. Casgevy costs $2.2 million per treatment. Zynteglo, a gene therapy for beta-thalassemia, is priced at $2.8 million. Lyfgenia, another sickle cell treatment, runs $3.1 million. These are among the most expensive medical treatments ever approved, and they create financial barriers that insurance systems and healthcare providers are still figuring out how to manage. For most people worldwide, direct DNA editing remains out of reach for now, even when a therapy technically exists for their condition.