germline mutation

A germline mutation is a change that occurs in the cells that give rise to eggs and sperm, so it can be handed down to a person's children. It is written into the copy of the genome that gets passed to the next generation, not just kept within one body.

Because the germline is the lineage of reproductive cells, a mutation present there will be carried in the egg or sperm that forms an offspring, and from that single cell it spreads to every cell of the new individual. The change therefore becomes a permanent part of that family line and can be inherited generation after generation.

Germline mutations are the basis of heritable genetic disorders and of the variation that evolution acts on across generations. They are contrasted with somatic mutations, which occur in non-reproductive body cells and stop with the individual. A new germline mutation that neither parent carried is called a de novo mutation.