The fragile X syndrome.
An amplification of a highly unstable DNA element has been identified at the fragile X locus in Xq27.3. This sequence appears to be both the source of the primary mutation causing the fragile X syndrome, apparently having its causative effect through the methylation of the FMR-1 HTF island and the region of cytogenetic fragility. The direct analysis of the genotype of carrier and affected individuals can be used as a direct diagnosis tool which will improve both the accuracy and speed of diagnosis. The identification of hereditary unstable DNA in a disease with such a wide level of non-penetrance and variable phenotype may give clues as to the basis of non-penetrance in other human genetic disorders.
Hirst
M C
MC
Knight
S J
SJ
Bell
M V
MV
Super
M
M
Davies
K E
KE
D002873:Chromosome Fragility; D004247:DNA / Q000235:genetics; D005260:Female; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000235:genetics*; D005784:Gene Amplification; D006580:Genetic Carrier Screening / Q000379:methods; D008040:Genetic Linkage; D005819:Genetic Markers; D006801:Humans; D008297:Male; D009154:Mutation / Q000235:genetics
D005819:Genetic Markers; D004247:DNA