Mutation

Definition

A mutation is a change in the DNA sequence of an organism.
Causes include:
- Errors during DNA replication in cell division.
- Exposure to mutagens (chemical or physical agents causing mutations).
- Viral infections.
Types of mutations:
- Germline Mutations: Occur in reproductive cells (eggs and sperm) and can be passed to offspring.
- Somatic Mutations: Occur in body cells and cannot be passed to offspring.

Mutations are frequent occurrences in cells but rarely affect health.
Contrary to science fiction, mutations do not result in superhuman abilities.
Factors mitigating mutation impacts:
- Cells have sophisticated repair mechanisms to fix mutations quickly.
- Most mutations occur in somatic cells, affecting only that cell and its descendants.
Germline mutations have wider implications as they affect every cell of an individual who develops from that egg or sperm.

Deletion: Part of DNA is lost or deleted.
Substitution: One base pair in DNA is replaced by another.
Point Mutation: A single nucleotide base change, insertion, or deletion in DNA.
Missense Mutation: A single nucleotide change results in a codon that codes for a different amino acid.

Narration by Daniel A. Gilchrist, Ph.D.
- Program Director, Division of Genome Sciences.
NHGRI - National Human Genome Research Institute
Updated: May 20, 2025.