Figure 1
From: Genome-wide analysis of alternative promoters of human genes using a custom promoter tiling array
Alternative promoters can take on several forms (A): Two promoters on a single exon (top); alternative first exons (middle); a downstream promoter is located within the intron region of another isoform (bottom). The median number of promoters per gene on our microarray is three (B). There are a significant number of single-promoter genes on the array, but these are invariably share a bidirectional promoter with multi-promoter genes.