Examples of IDs are Silver-Russell syndrome, displaying hypomethylation of the paternally imprinted locus H19/IGF2 in the 11p15 region, together with other alterations at chromosome 7 and 11 [89,90,91,92], Fragile X syndrome, most commonly caused by a trinucleotide repeat expansion “CGG”, within the promoter of the fragile X mental retardation 1 protein (FMR1), which leads to aberrant DNA methylation and gene silencing [93,94,95], and Angelman syndrome, with a frequency of 2–3%, caused by an imprinting defect in the expression of maternally expressed 15q11-q13 genes. The gene discussed is FMR1; the disease is fragile X syndrome.