Isochores and CpG islands in YAC contigs in human Xq26.1-qter.
GC levels were assessed at 37 loci across 30 Mb of Xq26.1-qter, a region physically mapped in overlapping yeast artificial chromosome clones. In 8 Mb of R band Xq26, GC is relatively high (up to 44%) in the proximal 4 Mb and relatively low (40-41%) in the distal 4 Mb. Consistently low GC values (38-41%) are observed in G band Xq27. In contrast, further toward the telomere in Xq28, the GC level rises progressively to reach 52% at 2 to 4 Mb from the end of the chromosome; this region is delimited by low GC loci. Across these regions of Xq, the content of rare-cutter restriction enzyme sites containing CpG, including "CpG islands" in the most completely mapped Xq26-27.1 region, is correlated with GC level. Isochore mapping can thus provide one index of putative gene content across mapped regions.
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Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110.
Little
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Aïssani
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Bernardi
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Schlessinger
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D002871:Chromosome Banding; D002874:Chromosome Mapping; D015825:Chromosomes, Fungal; D003001:Cloning, Molecular; D004247:DNA / Q000032:analysis / Q000235:genetics; D015342:DNA Probes; D015226:Dinucleoside Phosphates / Q000032:analysis*; D006367:HeLa Cells; D006801:Humans; D015183:Restriction Mapping; D014960:X Chromosome
D004247:DNA; D015342:DNA Probes; D015226:Dinucleoside Phosphates; C015772:CpG dinucleotide