English: Caption: "Overview of categories of variation including inherited (panels A–C), de novo (panels D,E), and somatic variation (panels F,G). Inherited mutations are always transmitted through the germline (A); although a parent may also have a mosaic mutation (this combination of somatic and germline mosaicism is occasionally termed gonadal mosaicism) (B); In such cases, a child may inherit the variant as a heterozygous mutation with a more severe clinical phenotype. A parent may also have germline mosaicism that may be inherited by progeny (C); De novo mutations are operationally defined as genotypes observed in a child but not in either parent. They may originate in a parental germ cell (as may be inferred in a pedigree having multiple affected offspring) (D) or postzygotically (E); Somatic mutation may occur relatively early in development (F) or at any later time throughout the lifespan (G), generally affecting fewer cells."