title: An evolutionary conserved early replicating segment on the sex chromosomes of man and the great apes.
abstract: Replication studies on prometaphase chromosomes of man, the chimpanzee, the pygmy chimpanzee, the gorilla, and the orangutan reveal great interspecific homologies between the autosomes. The early replicating X chromosomes clearly show a high degree of conservation of both the pattern and the time course of replication. An early replicating segment on the short arm of the X chromosomes of man (Xp22.3) which escapes inactivation can be found on the X chromosomes of the great apes as well. Furthermore, the most early replicating segment on the Y chromosomes of all species tested appears to be homologous to this segment on the X chromosomes. Therefore, these early replicating segments in the great apes may correspond to the pseudoautosomal segment proposed to exist in man. From further cytogenetic characterization of the Y chromosomes it is evident that structural alterations have resulted in an extreme divergence in both the euchromatic and heterochromatic parts. It is assumed, therefore, that, in contrast to the X chromosomes, the Y chromosomes have undergone a rapid evolution within the higher primates.
mesh_terms: D000818:Animals; D005075:Biological Evolution; D001973:Bromodeoxyuridine / Q000494:pharmacology; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D002871:Chromosome Banding; D004261:DNA Replication / Q000187:drug effects; D005260:Female; D006071:Gorilla gorilla / Q000235:genetics*; D000882:Haplorhini / Q000235:genetics*; D015186:Hominidae / Q000235:genetics*; D006801:Humans; D008214:Lymphocytes / Q000166:cytology; D008297:Male; D002679:Pan troglodytes / Q000235:genetics*; D011148:Pongo pygmaeus / Q000235:genetics*; D012730:Sex Chromosomes; D013045:Species Specificity; D014960:X Chromosome; D014998:Y Chromosome
chemical_list: D001973:Bromodeoxyuridine