Most variants do not lead to development of disease, and those that do are uncommon in the general population. Some variants occur often enough in the population to be considered common genetic variation. Several such variants are responsible for differences between people such as eye color, hair color, and blood type.
Are mutation always heritable?
If an acquired mutation occurs in an egg or sperm cell, it can be passed down to the individual's offspring. Once an acquired mutation is passed down, it is a hereditary mutation. Acquired mutations are not passed down if they occur in the somatic cells, meaning body cells other than sperm cells and egg cells.
How often are mutations inherited?
Recently reported estimates of the human genome-wide mutation rate. The human germline mutation rate is approximately 0.5×10−9 per basepair per year.
