Roberts' syndrome. I. Cytological evidence for a disturbance in chromatid pairing

In the rare developmental disorder Roberts' syndrome, prophase and metaphase chromosomes display premature sister-chromatid separation, most prominently at certain regions in which the chromatin is composed of highly reiterated base sequences. In addition, interphase nuclei present a striking distortion in their contours. The observed abnormalities are interpreted as evidence for the presence of a genetically determined disturbance affecting the normal mechanisms for pairing and disjoining of sister chromatids.