The fragile X syndrome.

1. Introduction 293 2. Clinical and cytogenetic features 293 3. Isolation of the gene associated with fragile X syndrome 295 4. The nature of the trinucleotide repeat 295 5. The FMR1 gene 298 6. A possible role for FMR1 298 7. Expression studies 299 8. Trinucleotide repeats and human disease 300 9. Prospects 301 10. Note added in proof: 301 References 301