Figure 2 - Polyacrylamide gel electrophoresis of the products of methyla-tion- specific PCR of the human FMR1 gene on the X chromosome. Met. FMR is the 142-bp fragment from the bisulfite-treated methylated CpG is-land, while N/Met. FMR is the 84-bp product from the treated non-meth-ylated promoter. Maternal SNRPN is 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, a normal man and a patient with the fragile X syndrome diagnosed by chromosomal studies and Southern blot analysis were treated with sodium bisulfite as described by Herman et al. (1996). On the rightmost lane of the gel are the 123-bp ladder molecular size standards (Life Technologies, Gaithersburg, MD, USA).