gene editing

Gene editing means precisely changing a specific stretch of DNA inside a living cell — rewriting one passage of the genome rather than the whole book. Where older gene therapy mostly added an extra copy of a gene, editing goes to the original text and alters it directly: correcting a misspelled letter, deleting a broken word, or pasting in a fix exactly where it belongs.

It relies on molecular tools that can be aimed at a chosen DNA address. CRISPR is the best-known, but earlier toolkits called TALENs and zinc-finger nucleases work on the same idea: a targeting part that recognises the right sequence, joined to a cutting part that lets the change be made. The cell's own repair machinery then locks in the edit, and the cell carries the new version forward.

Because it changes the source instructions, editing can in principle make a lasting correction with a single treatment. The hard parts are aiming perfectly so nothing else is altered, reaching enough of the right cells, and — for any edit that could be inherited — answering the heavy ethical questions before it ever nears the clinic.