FIGURE 1.

Occurrence of somatic mutations and their identification in next-generation sequencing data. (A) Somatic mutations that occur postzygotically after fertilization. Mutations arising during embryogenesis or under clonal expansion (green and blue) are shared in a fraction of the cell population, whereas mutations accumulating during the aging process (purple) may only be present in a single cell. (B) Identification of somatic mutations using bulk or single-cell sequencing. Bulk sequencing is suitable for detecting somatic mutations shared across multiple cells, though mutations with low allele fractions are difficult to distinguish from sequencing errors. Private somatic mutations can be detected with single-cell sequencing, but the whole-genome amplification before sequencing may introduce additional artifacts resulting from amplification errors.