REPLICATION PATTERNS OF SEX-CHROMOSOMES IN MELANDRIUM-ALBUM FEMALE CELLS

Autoradiographic analysis of chromosome replication patterns in heterogametic male and homogametic female hairy-root cell lines of a dioecious plant, Melandrium album, has shown an early replication of the only X and a conspicuous difference between the two X chromosomes, respectively. This divergence could be significantly reduced by a 5-azacytidine treatment, thus confirming our recently published results on the different degree of DNA methylation of the X chromosomes in female cells. The early replicating and aberration prone X chromosome seems to be less condensed, too. [H-3]thymidine labelling patterns as well as [H-3]uridine induced chromosome aberrations do not indicate any differences between the long and short arms of the X chromosomes. The presented data support the hypothesis that one of the two X chromosomes in M. album female cells could be inactivated and hypermethylated as described in mammals.