difference in gene expression in vitro (Edenberg et al. 1999). For the ADH1C gene, expression differs by 40 percent between various haplotypes in a regulatory element located from 3,910 to 3,496 bp upstream of the transcription start site; in addition, a particular combination of three SNPs and a 66-bp insertion/deletion in a region located from 3,496 to 3,008 bp upstream of the gene is associated with a two-fold difference in gene expression (Chen et al. 2005). The effects of other noncoding polymorphisms on gene expression still need to be studied.
