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How can mutations in egg cells or sperm cells be passed to offspring?

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BRCA2 tumor suppressor gene on chromosome 13 — human genetic disease Photomicrograph of the *BRCA2* tumor suppressor gene on chromosome 13 of the human genome. Inactivation of this growth-regulating gene is associated with a higher risk of developing breast cancer.

Mutations in egg or sperm cells, known as germinal mutations, are passed to offspring because these cells—collectively called gametes—carry the genetic blueprint that forms the next generation.12

During the process of meiosis, cells undergo division to produce gametes that contain only half the number of chromosomes found in typical body cells. When a mutation occurs within the DNA of these reproductive cells, that altered genetic information is incorporated into the zygote upon fertilization. Because this mutation is present at the very beginning of the offspring's development, it is replicated into all of the individual's cells.314

While some mutations are inherited from parents who carry the trait, others may arise spontaneously for the first time during the formation of the gametes themselves. Once a germinal mutation is passed on, it can be transmitted to subsequent generations, serving as a fundamental source of genetic variation or, in many cases, leading to human genetic disease.142