Germline mutation

A germline mutation, or germinal mutation, is any detectable variation within germ cells (cells that, when fully developed, become sperm and ova).^[1] Mutations in these cells are the only mutations that can be passed on to offspring, when either a mutated sperm or oocyte come together to form a zygote.^[2] After this fertilization event occurs, germ cells divide rapidly to produce all of the cells in the body, causing this mutation to be present in every somatic and germline cell in the offspring; this is also known as a constitutional mutation.^[2] Germline mutation is distinct from somatic mutation.

Germline mutations can be caused by a variety of endogenous (internal) and exogenous (external) factors, and can occur throughout zygote development.^[3] A mutation that arises only in germ cells can result in offspring with a genetic condition that is not present in either parent; this is because the mutation is not present in the rest of the parents' body, only the germline.^[3]