Is DNA repair really possible? At first glance, the idea of repairing or changing DNA sounds like something from a science fiction movie. Yet everything in the universe, including the DNA molecule, is built on basic chemical structures that break down into smaller and simpler particles. Because DNA, or deoxyribonucleic acid, is made primarily of amino acids, modifying genetic codes on a nanoscale level is not only possible but also understandable once the logic behind it is clear. Even with our still limited understanding of cells and genetics, humanity has reached the point of using tools such as CRISPR-Cas9, which work through basic principles like cutting, trimming, and separating nucleotides.
A few years ago, molecular biochemist Jennifer Doudna and her colleague Emmanuelle Charpentier developed a new way to edit genomes. Doudna named it CRISPR-Cas9, inspired by a natural defense mechanism found in bacteria. When a bacterium survives a viral attack, it saves a piece of the virus’s genetic information in its memory. If the same virus attacks again, the bacterium’s RNA copies that stored information and passes it to a special protein called Cas9. This protein scans genetic material, finds a perfect match with the viral DNA, and cuts the strand, protecting the cell from infection.
Tests with mice and monkeys have shown that CRISPR can successfully modify DNA. Researchers in China later used the technique on human embryos, while scientists in Philadelphia applied it to remove HIV DNA from infected cells. Once the DNA is cut, the repair process begins in one of two ways. The first method is the cell’s emergency response: it quickly reconnects the broken ends of DNA, roughly patching the strand back together. The second method occurs in sexually reproducing organisms such as humans. Since we inherit two copies of each gene, one from each parent, the damaged section can be repaired using the healthy copy as a template. This process carries less risk and produces fewer errors. The possibility of applying these repair mechanisms intentionally to human DNA has inspired both excitement and concern. Some see it as a step toward curing disease and extending life, while others worry about the ethical implications of redesigning what nature created.
From the discovery of DNA onward, people have been fascinated by the idea of altering it. The story stretches from random radiation-induced mutations in the 1960s to genetically modified crops in the 1990s and even to experiments with embryos that carry genetic material from three parents. What sets CRISPR apart is its simplicity. It reduces the cost and time needed for genetic modification so effectively that even laboratories with modest resources can use it. The technology has brought ideas such as designer babies and enhanced immunity much closer to reality.
Programming CRISPR involves introducing a copy of the DNA sequence that will be modified into the system, which is then inserted into a living cell. Its low cost and flexibility allow researchers to apply it to almost any organism. It has already been used to remove viruses such as HIV and Herpes from cells and to reprogram immune cells to attack cancer. When China and the United States approved CRISPR for human trials in 2016, it marked the beginning of a new era. The ability to rewrite the genetic future of living beings is no longer a distant dream. It is something that can now be done, quite literally, by hand.