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Replication Timing, Chromosomal Bands, and Isochores
Maria Costantini and Giorgio Bernardi
Proceedings of the National Academy of Sciences of the United States of America
Vol. 105, No. 9 (Mar. 4, 2008), pp. 3433-3437
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/25461252
Page Count: 5
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Chromosome replication timing is biphasic (early-late) in the cell cycle of vertebrates and of most (possibly all) eukaryotes. In the present work we have compared the extended, detailed replication timing maps that are available, namely those of human chromosomes 6, 11q, and 21q, with chromosomal bands as visualized at low (400 bands), high (850 bands), and highest (3,200 isochores) resolution. We have observed that the replicons located in a given isochore practically always show either all early or all late replication timing and that early-replicating isochores are short and GC-rich and late-replicating isochores are long and GC-poor. In the vast majority of cases, replicons are clustered in isochores, which are themselves most often clustered in early- or late-replication timing zones and may often reach the size of high-resolution bands and, very rarely, even that of low-resolution bands. Finally, we show that our results should be representative for the whole human genome and thus help to predict replication timing zones in all chromosomes.
Proceedings of the National Academy of Sciences of the United States of America © 2008 National Academy of Sciences