Genomic structure and locations of single nucleotide polymorphisms inAPOE. (a) The exon-intron structure. (b) The distribution of mapped protein-binding sites in the 5′ flanking sequence and first intron. (c) The types and distribution of repeat sequences. (d) DNA variants identified by sequencing 72 individuals. Coding-region variants are boxed. (e) Percentage identity plot for a comparison of human and mouse genomic sequences for APOE. The regions associated with the exons are indicated by number (1–4). The two regions associated with enhancer activities are indicated by letter (a or b).