What causes the abnormal phenotype in a 49,XXXXY male?

✍ Scribed by Gloria E. Sarto; Priscila G. Otto; Evelyn M. Kuhn; Eeva Therman

• Publisher: Springer
• Year: 1987
• Tongue: English
• Weight: 725 KB
• Volume: 76
• Category: Article
• ISSN: 0340-6717
• DOI: 10.1007/bf00283041

✦ Synopsis

The chromosome replication pattern of a man with 49,XXXXY was analyzed using 3H-thymidine and autoradiography as well as BrdU and acridine orange. The former technique showed a highly irregular replication pattern; the latter revealed one early replicating X chromosome, and the other three more or less asynchronously replicating. Two hypotheses seem to explain best the abnormal phenotype of males with an XXXXY sex chromosome constitution: The number of the always active regions (tip of Xp) and of the possibly always active regions (the Q-dark regions on both sides of the centromere) is increased from one to four. The replication pattern of the late-replicating X chromosomes is highly asynchronous, which might affect the phenotype. The possibility that more than one X chromosome might remain active in some cells, an even more abnormal and obviously deleterious situation, is still open.