# Mutation

A random change in the DNA of a gene. Most are harmless, some are harmful and a few are useful.

Biology (school) · Part 06: Variation and evolution · Card 2 of 11 · Last updated 2026-10-19

## Analogy

A typo in a recipe. Mostly it makes no difference, sometimes it ruins the dish, rarely it improves it.

## In practice

A mutation made some bacteria resistant to an antibiotic.

## Practice

### Flashcards

- **What is a mutation?** A random change in the DNA sequence of a gene.

## Questions people ask

### Are all mutations bad?

No. Most mutations do nothing because they change a part of the DNA that is not important or give the same protein. Some are harmful and can cause disease. A few help the organism, for example by making a bacterium resistant to an antibiotic, and natural selection can then favour them.

### What causes mutations?

Mutations happen by chance when DNA is copied, but the rate increases with ionising radiation such as X-rays, ultraviolet light and some chemicals. These are called mutagens. Mutations in body cells can lead to cancer, but only mutations in sex cells can be passed to children.

## Related concepts

- [Variation](https://studyvisually.com/learn/science/biology-school/biology-school-part-6/biology-school-part-6-concept-1)

Web page: https://studyvisually.com/learn/science/biology-school/biology-school-part-6/biology-school-part-6-concept-2
Study this card in the app: https://studyvisually.com/app/learn?category=biology-school&card=biology-school-part-6-concept-2