Abstract
The human genome is often viewed as a stable collection of genes, embedded both in the DNA necessary to regulate their expression and in the chromosomal packaging. According to this relatively static picture, genetic diseases may be caused by rare mutation events that damage a gene, deleting a portion or altering its coding sequence. However, the human genome is also populated by DNA sequences that are not at all static, but vary with considerable frequency. This issue of the Journal presents an example of one such sequence, particular variants of which are associated with an increased risk of cancer1. . . .