New informative polymorphism at the DXS304 locus, a close distal marker for the fragile X locus.
The polymorphic DNA marker DXS304 detected by probe U6.2 has recently been shown to be closer to the fragile X locus than previously available markers. Its usefulness has however been limited by its relatively low heterozygosity. We have isolated, by cosmid cloning, a 67 kilobase region around probe U6.2 and have characterized a new probe (U6.2-20E) that detects BanI and BstEII restriction fragment length polymorphisms (RFLPs). The BanI RFLP has a heterozygosity of 0.49 and is in partial linkage disequilibrium with the previously described polymorphism, with a combined heterozygosity of 0.63. Furthermore, we have found that the U6.2 original probe, which probably detects an insertion-deletion polymorphism, is also informative in BanI digests. Thus, the two informative RFLPs at the DXS304 locus can be conveniently tested in a single hybridization with a single digest. An updated linkage analysis confirms that DXS304 is distal to the fragile X locus. This informative locus can now be used effectively for genetic mapping of the Xq27-q28 region, and for diagnostic applications in fragile X or Hunter syndrome families.
Rousseau
F
F
Laboratoire de Génétique Moléculaire des Eucaryotes du CNRS, Faculté de Médecine, Strasbourg, France.
Vincent
A
A
Oberlé
I
I
Mandel
J L
JL
D015139:Blotting, Southern; D015342:DNA Probes; D005260:Female; D005600:Fragile X Syndrome / Q000235:genetics*; D005819:Genetic Markers; D006801:Humans; D008297:Male; D010375:Pedigree; D012150:Polymorphism, Restriction Fragment Length; D012729:Sex Chromosome Aberrations / Q000235:genetics*
D015342:DNA Probes; D005819:Genetic Markers