X‐linked mental retardation with macro‐orchidism and marker‐X chromosomes

Publisher Website
Google Scholar
Abstract
The family of 2 men with X‐linked mental retardation was investigated for the presence of the marker‐X chromosome and macro‐orchidism. Lymphocyte cultures were set up in media F‐10 and 199. Chromosomes were G‐band‐stained and slides coded for blind analysis. Marker‐X chromosomes and autosomal gaps were seen only in cultures prepared with medium 199. Autosomal gaps were seen in all family members and controls. The marker‐X chromosome was present in affected male (3% and 15.5%) and female family members (0.5%–6.5%) but not in controls or a normal male family member. Bilateral macro‐orchidism was present in 1 affected male and unilateral macro‐orchidism in the other. Both had normal penile measurements. The replication pattern of the marker‐X chromosome was studied in 1 woman by BrdU labelling. BrdU decreases the frequency of marker‐X expression. As the marker‐X chromosome was the late‐replicating X in 9/20 cells, it appears that there is no preferential inactivation of the marker‐X in this woman.