This study was undertaken to provide cytogenetic information about onset and sequence of RBA-band replication on the inactive X-chromosomes of cattle, river buffalo and goat. Blood cultures were synchronized overnight with thymidine after 48 hours of growth. The cell block was released with fresh medium and the cells allowed to continue their growth in the presence of BrdU and H33258. The cultures were harvested after 1, 2, 4, 6, 8, 10, 12 and 14 hours, including 20 minutes Colcemide, and treated for RBA-banding. Results show that: (a) the onset of RBA-banding replication was found to be around 12 hours before mitosis in cattle and river buffalo, 14 hours in the goat; (b) the replication process was still on in cattle and river buffalo one hour before mitosis, whereas it was off in the goat; (c) the length of the G2 phase was found negligible, i.e. less than one hour, in cattle and river buffalo, while it was one hour -or slightly longer- in the goat; (d) the first band undergoing replication was identified as band Xq31 in cattle, homologous to band Xq34-36 in river buffalo and Xq24 in the goat; this band was considered as the first and major replication center (RCI); (e) the second replicating band was the Xp22 in cattle, homologous to band Xq21 in river buffalo and Xq34 in the goat, respectively; this band was considered as the second replication center (RCII); (f) the sequence of RBA-band replication was quite similar between cattle and river buffalo, but reversed in the goat, due to the wide chromosomal rearrangements which differentiated the X-chromosome of Caprinae from that of Bovinae.
Onset and sequenze of RBA-band replication on the inactive X-chromosomes of cattle (Bos taurus L.), river buffalo (Bubalus bubalis L.) and goat (Capra hircus L.).
2002
Abstract
This study was undertaken to provide cytogenetic information about onset and sequence of RBA-band replication on the inactive X-chromosomes of cattle, river buffalo and goat. Blood cultures were synchronized overnight with thymidine after 48 hours of growth. The cell block was released with fresh medium and the cells allowed to continue their growth in the presence of BrdU and H33258. The cultures were harvested after 1, 2, 4, 6, 8, 10, 12 and 14 hours, including 20 minutes Colcemide, and treated for RBA-banding. Results show that: (a) the onset of RBA-banding replication was found to be around 12 hours before mitosis in cattle and river buffalo, 14 hours in the goat; (b) the replication process was still on in cattle and river buffalo one hour before mitosis, whereas it was off in the goat; (c) the length of the G2 phase was found negligible, i.e. less than one hour, in cattle and river buffalo, while it was one hour -or slightly longer- in the goat; (d) the first band undergoing replication was identified as band Xq31 in cattle, homologous to band Xq34-36 in river buffalo and Xq24 in the goat; this band was considered as the first and major replication center (RCI); (e) the second replicating band was the Xp22 in cattle, homologous to band Xq21 in river buffalo and Xq34 in the goat, respectively; this band was considered as the second replication center (RCII); (f) the sequence of RBA-band replication was quite similar between cattle and river buffalo, but reversed in the goat, due to the wide chromosomal rearrangements which differentiated the X-chromosome of Caprinae from that of Bovinae.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
