Two brothers with mental retardation discordant for the fragile-X syndrome.
We describe two male sibs with mental retardation discordant for the fragile-X syndrome. In the younger sib, chromosome analysis under folate deprivation showed a fragile site at Xq27.3 in 12-46% of mitoses. In the older sib, however, repeated chromosome analyses (six different cultures with analysis of 50 mitoses each) under identical conditions could not detect any fragile-X site. Using DNA probes linked to the fragile-X gene, we found evidence that the two sibs inherited a different maternal X chromosome at Xq27.3. This excluded the presence of the fragile-X syndrome in the older sib with a probability of greater than 99%.
Van Roy
B C
BC
Department of Medical Genetics, University of Antwerp-UIA, Wilrijk, Belgium.
Willems
P J
PJ
Vits
L J
LJ
Ceulemans
B P
BP
Coucke
P J
PJ
Van der Auwera
B J
BJ
Lormans
J A
JA
Dumon
J E
JE
D000328:Adult; D002648:Child; D004247:DNA / Q000032:analysis; D015342:DNA Probes; D005600:Fragile X Syndrome / Q000235:genetics*; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics*; D008297:Male; D010375:Pedigree; D010641:Phenotype; D012729:Sex Chromosome Aberrations / Q000235:genetics*
D015342:DNA Probes; D004247:DNA