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Mutations: changes in genetic information — Biology, 14–17 years

A mutation changes a DNA sequence. It may have no visible effect, or it may alter a protein and influence an organism’s traits or survival.

Idea

A mutation is a change in the DNA letters of a cell. It can happen when DNA is copied, or after damage such as ultraviolet light, and cells sometimes repair it. Most mutations do little, but some change a protein or the way a gene is used.

Why it matters

Without mutations, DNA copies would stay exactly the same and populations would have little new variation. That would make adaptation to a changing environment much harder. Mutations are not made because an organism needs them: they appear without planning, and selection may later favour or remove their effects.

Worked example

Imagine a DNA sequence with the letters A, C, G, T, T, A. During copying, the fourth letter changes from T to C, giving A, C, G, C, T, A. If that sequence belongs to a gene, the change may alter one protein building block; the protein might work normally, work differently, or stop working.

Common trap

It is tempting to call every mutation harmful because the word often appears in stories about disease. But a DNA change can be neutral, helpful, or harmful, depending on where it occurs and the environment. A mutation in a non-working stretch may change nothing at all.

Outside school

Doctors and researchers compare mutations when studying inherited conditions and cancer, because some changes help cells grow out of control. Scientists also track mutations in viruses to see how populations change over time. A mutation alone does not prove that a disease will appear; its effect depends on the gene and the person’s biology.

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