Heterozygous female carriers of the marker-X-chromosome: IQ estimation and replication status of fra(X)(q).
The IQ levels of 18 female carriers with the marker X chromosome were evaluated, and cytogenetic studies after BrdU incorporation were performed. A highly significant correlation between mental capacity and replication pattern of the X chromosomes could be demonstrated. Heterozygous females with normal intelligence showed a clear tendency to carry the fragile site at the late replicating X chromosome, while other female carriers with lower intelligence or mental impairment expressed their fragile site mainly with the early replicating X chromosome. This observation could be interpreted as an expression of Lyonisation .
D000293:Adolescent; D000328:Adult; D002675:Child, Preschool; D004261:DNA Replication; D004303:Dosage Compensation, Genetic; D005260:Female; D005600:Fragile X Syndrome / Q000235:genetics*; D005819:Genetic Markers; D006579:Heterozygote; D006801:Humans; D007361:Intelligence Tests; D008214:Lymphocytes / Q000648:ultrastructure; D008875:Middle Aged; D012729:Sex Chromosome Aberrations / Q000235:genetics*
D005819:Genetic Markers