Mammalian sex chromosomes. IV. Replication heterogeneity in the late replicating facultative- and constitutive-heterochromatic regions in the X chromosomes of the mole rats, Bandicota bengalensis and Nesokia indica.
The karyotypes of Nesokia indica and Bandicota bengalensis are identical except for their sex chromosomes, which are much larger in Nesokia due to additional constitutive heterochromatin (C.H.). Replication patterns of their sex chromosomes were studied employing 3H-Tdr autoradiography and BrdUrd-FPG staining techniques. Though the "conservative" part of both early- and late-replicating X chromosomes revealed identical replication patterns in most cells, deviant patterns of only the late replicating X chromosome were encountered in approximately 10% cells. Surprisingly, these late-X variants were similar in the two species. The sex chromosome-associated C.H. segments replicated late in S-phase and, in females, the homologous heterochromatin replicated asynchronously--the later replicating one was predominantly associated with the late X. These results suggest structural and functional conservation of the X chromosomes as well as the possible influence of facultative heterochromatin (F.H.) on the replication of associated C.H. in these two species.
Dubey
D D
DD
Department of Zoology, Banaras Hindu University, Varanasi, India.
Raman
R
R
D000818:Animals; D001854:Bone Marrow Cells; D004261:DNA Replication; D006570:Heterochromatin / Q000502:physiology*; D008297:Male; D009115:Muridae / Q000235:genetics*; D012867:Skin / Q000166:cytology; D013154:Spleen / Q000166:cytology; D013936:Thymidine / Q000378:metabolism; D014960:X Chromosome; D014998:Y Chromosome
D006570:Heterochromatin; D013936:Thymidine