XYY chromosomal complement,proven by fluorescence,in a child with trisomy 21: 48,XYY,21+

Summary Clinical, cytogenetic, autoradiographic, fluorescence microscopic and dermatoglyphic data of a boy with 48,XYY,21+ karyotype are reported. The child had some clinical anomalies common in Down's syndrome. DNA replication of the 2 Y chromosomes was synchronous in all labelled metaphases. It was possible to distinguish the two Y's from the pairs No. 21-22 under the fluorescence microscope and single as well as double Y bodies were demonstrated in buccal mucosa cells. Dermatoglyphic investigation revealed some features typical for mongolism.