A possible exception to the critical region hypothesis.
Cytogenetic studies were done on a 5-year-old female with multiple congenital anomalies and mental retardation, revealing an unbalanced X/11 translocation. Her mother and phenotypically normal sister carry the balanced form of the translocation, while her brother has a normal 46,XY karyotype. Banding studies showed the breakpoints to be Xq22 and 11q13. These are remarkable for the following reasons: (1) the X breakpoint is within the critical region of the X chromosome, yet the balanced carrier does not manifest gonadal dysgenesis; and (2) the proband was trisomic for most of the long arm of chromosome 11. Late-replication studies of cells from the two balanced carriers showed inactivation of the normal X.
D000015:Abnormalities, Multiple / Q000235:genetics*; D002675:Child, Preschool; D002871:Chromosome Banding; D002906:Chromosomes, Human, 6-12 and X; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics*; D007621:Karyotyping; D012730:Sex Chromosomes; D014178:Translocation, Genetic; D014960:X Chromosome