Long range genome structure around the human α-globin complex analysed by PFGE

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Abstract
A map encompassing 300 kilobases (kb) in and around the human α-globin gene complex shows features with important implications for understanding the structure and function of the human genome. In contrast to other segments of the mammalian genome that have been analysed by pulsed field gradient electrophoresis (PFGE), this region contains an unusually high density of sites for infrequently cutting restriction enzymes that recognise GC rich motifs including the under-represented CpG doublet. This suggests that the 2b kilobase (kb) stretch of DNA containing the α-globin gene family, which is known from sequence analysis to be 60% GC rich, is itself embedded within a region of high GC content. This long-range structure, identified by PFGE, fnonds to a class of GC rich isochores that are thought to represent early replicating DNA present in Giemsa negative chromosomal bands. The identification or such regions by PFGE will be of value in understanding the organisation of human chromosomes and will influence the strategies used to construct a physical map of the genome.