Translocation X sur autosome et replication tardive

A patient with ovarian failure was found to have a segment of the long arm of an X chromosome translocated to the distal end of the short arm of a 2nd chromosome: 46,X,t(X;2)(q21;p25). The Barr bodies were of normal size. Autoradiographic and B.U.D.R. studies showed that the normal X was the late-replicating X. The translocated segment was late replicating in 5% without spreading effect. It is suggested that preferential inactivation of the normal X chromosome is observed when a segment of X chromosome is translocated onto an autosome. When a segment of autosome is translocated onto an X chromosome, the abnormal X chromosome is consistently late-replicating. These findings may be available for other mammalian species in the balanced translocations.