Erratum
In the report "Isolation of sequences that span the fragile X and identification of a fragile X-related CpG island" by D. Heitz et al. (8 Mar., p. 1236), in the first line of figure 1 ("Chromosomal breakpoints"), PeCH should not have appeared. The breakpoint indicated corresponds to the APC5 cell line described by G. K. Suthers et al. [Am. J. Hum. Genet. 47, 187 (1990)].