title: Late DNA replicaion of X chromosomes in female and pseudofemale cells of Microtus agrestis.
abstract: The late replication pattern of the short arms of the X chromosomes of Microtus agrestis was studied in female cells and in cells with 2 X chromosomes of male origin by means of the BUdR-Giemsa technique and of 3H-thymidine labelling. The light absorption of Giemsa stained chromosome sections which were unifilarly substituted with BUdR (labelled), was found to be 59.2% of that of unlabelled chromosomes. In female cells, asynchrony of DNA replication of both X chromosomes indicated the presence of facultative heterochromatin in the X2 and euchromatin in the X1. In the male cells only euchromatic X chromosomes were observed in diploid XX and XO cells as well as in triploid XXY, XX and XO cells. The results show that inactivation of an X chromosone in vitro, in cells with more than one originally active X chromosome does not occur even after a culture duration of several years.
mesh_terms: D000818:Animals; D003411:Arvicolinae / Q000378:metabolism*; D001973:Bromodeoxyuridine; D004261:DNA Replication; D005260:Female; D006570:Heterochromatin / Q000378:metabolism; D008297:Male; D008938:Mitosis; D011123:Polyploidy; D012377:Rodentia / Q000378:metabolism*; D012728:Sex Chromatin / Q000378:metabolism; D012730:Sex Chromosomes / Q000378:metabolism*; D013194:Staining and Labeling; D013997:Time Factors
chemical_list: D006570:Heterochromatin; D001973:Bromodeoxyuridine