Mutation
A mutation is a change in genetic sequence. Mutations can happen during DNA copying, after DNA damage, or through larger chromosome changes, and they can be neutral, harmful, beneficial, inherited, or limited to particular cells.
What a mutation is
A mutation is a change in genetic sequence. It may affect one DNA base, several bases, a whole gene, or a large chromosome region. Mutations are often discussed as mistakes, but in biology they are simply sequence changes; their effects depend on where they occur and what they change.
How mutations happen
Mutations can arise when DNA is copied and a mismatch escapes proofreading and repair. They can also follow DNA damage from ultraviolet light, radiation, chemicals, or normal cellular chemistry. Some mutations come from mobile DNA elements, chromosome breaks, or errors during cell division.
Point mutations and small changes
A point mutation changes a single DNA base. Other small changes insert or delete a few bases. In a protein-coding gene, a base substitution may be silent, change one amino acid, or create a stop signal. Insertions or deletions can shift the reading frame unless their length is a multiple of three bases.
Larger genome changes
Not every mutation is tiny. Duplications, deletions, inversions, translocations, and copy-number changes can alter larger DNA segments. These changes may remove genes, add extra copies, move genes near new regulatory regions, or change chromosome structure.
DNA repair
Cells have repair systems that detect many forms of DNA damage or copying error. Mismatch repair, base excision repair, nucleotide excision repair, and double-strand break repair help protect genomes. Repair is powerful but not perfect, so some changes become permanent mutations after DNA is copied.
Somatic and germline mutations
Somatic mutations occur in body cells. They can contribute to cancer or mosaicism, but they usually are not inherited by children. Germline mutations occur in eggs, sperm, or their precursor cells. If passed to offspring, they become part of that person's genome from the first cell onward.
Effects on traits
Some mutations have little or no effect because they occur outside sensitive regions or do not change function. Others alter proteins, RNA molecules, regulatory DNA, or chromosome organization. A mutation's effect can depend on the organism's environment, genetic background, and whether one or both gene copies are affected.
Mutation and evolution
Mutation creates new genetic variation. Natural selection, genetic drift, migration, and recombination then influence how variants spread or disappear in populations. Without mutation, evolution would have far less raw material for adaptation and diversity.
Why it matters
Mutations matter in medicine, ancestry, agriculture, conservation, pathogen surveillance, and biotechnology. They help explain inherited disorders, cancer development, antibiotic resistance, viral evolution, crop traits, and the differences that make genomes unique.