Nonredundant exon clusters of 2,216,993 spliced EST (best placement), 36,164 known genes, and 22,933 RefSeq genes that have intron–exon structures are placed in either duplication or unique regions in the human genome. Each transcription unit was only counted once in this analysis. The duplicate and unique regions in the human genome (May 2004) correspond to 153.99 and 2712 Mb, respectively, while the transcribed portions of the duplicate and unique regions are 76.78/1328.4 Mb in ESTs, 28.56/871.22 Mb in known genes, and 24.63/847.85 Mb in RefSeq genes.