A complex mutable polymorphism located within the fragile X gene.
While studying founder chromosomes in the fragile X syndrome, we have unexpectedly found linkage equilibrium to FRAXAC2, an Alu-associated microsatellite within the defective gene, FMR-1. DNA sequencing of 265 chromosomes revealed 39 alleles and a complex microsatellite of form (GT)x-C-(TA)y-(T)z. A mutation rate of 3.3% was observed but only among fragile X maternally derived meioses. Finding a second mutable locus within FMR-1 suggests that the target for tandem repeat instability may not be confined to the (CGG)n repeat alone and raises the possibility of an FMR-1 mutation mechanism involving microsatellites.
Zhong
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N
Department of Human Genetics, New York State Institute for Basic Research in Developmental Disabilities, Staten Island 10314.
Dobkin
C
C
Brown
W T
WT
D001483:Base Sequence; D002873:Chromosome Fragility; D004276:DNA, Satellite; D005260:Female; D005600:Fragile X Syndrome / Q000235:genetics*; D005819:Genetic Markers; D006801:Humans; D015810:Linkage Disequilibrium; D008297:Male; D008540:Meiosis / Q000235:genetics; D008969:Molecular Sequence Data; D010375:Pedigree; D011110:Polymorphism, Genetic; D012091:Repetitive Sequences, Nucleic Acid
D004276:DNA, Satellite; D005819:Genetic Markers