Polyacrylamide gel electrophoresis of the products of MSP of the human FMR1 gene on the X chromosome. Methyl. FMR indicates the 142-bp fragment from the bisulfite-treated methylated CpG island; Non-methyl. FMR, the 84-bp product from the treated nonmethylated promoter; Maternal SNRPN, the internal control 174-bp product of amplification of the imprinted maternal methylated version of the CpG island of the SNRPN gene on human chromosome 15 (Kubota et al, 1997). DNA samples from a normal woman (46,XX), a normal man (46,XY), and a patient with Klinefelter syndrome (47,XXY) previously diagnosed by chromosomal studies are shown. The diagnosis of Klinefelter syndrome is indicated by the presence in a male patient of the 142-bp product characteristic of the inactive (methylated) X chromosome. On the rightmost lane of the gel are molecular size standards.