What is a mutation?
A mutation is a permanent change in the letters of DNA, like a typo that gets copied into every future edition of a recipe.
Imagine copying a cookbook by hand, millions of times. Sometimes you write "salt" where it said "sugar". Most typos land somewhere harmless. Occasionally one ruins a recipe that really matters.
Why it matters for aging
Every time a cell copies its DNA, there's a tiny chance of a mistake. Repair systems catch almost all of them, but not quite all. Over decades, each cell slowly collects its own unique set of typos.
That slow build-up is one reason aging tissue works a little less well, and it's part of why the risk of cancer rises with age. The DNA inside mitochondria, the cell's power plants, collects typos even faster than the main DNA in the nucleus.
A common myth
Mutations are things you're born with, and they're always bad.
Most of your mutations appear during your lifetime, not at birth, from copying mistakes and damage such as sunlight or smoking. The vast majority do nothing noticeable. A few, in the wrong place, can disrupt how a cell works.
Go deeper
Deep dives
Related terms
Updated Nov 7, 2026 · All terms