OPRL1 is located on chromosome 20q13 and has alternative splicing transcript variants that are controlled by alternate-promoter mechanism and contain 4 or 5 exons (Ito et al. 2000; Wick et al. 1995). The protein is encoded by three exons. Seventeen coding SNPs have been described, of which only the synonymous SNP rs2229205 is common in several populations.
