Due to increased production of human DNA sequence, it is now possible to explore and understand human genomic organization at the sequence level. In particular, we have studied one of the major organizational components of vertebrate genome organization previously described as isochores (Bernardi, 1993), which are compositionally homogeneous DNA segments based on G+C content. We have examined sequence data for the existence of compositionally differing regions and report that while compositionally homogeneous regions are present in the human genome, current isochore classification schemes are too brad for sequence-level data
