PCR-RFLP assay for SNP genotyping. Schematic representation of the PCR-RFLP assay used for genotyping a biallelic SNP [entrezSNP: rs24602000] in the canine serotonin transporter gene (SLC6A4). A 135-bp fragment encompassing the SNP is amplified by PCR and subsequently digested with the EcoRI restriction endonuclease. The C allele creates the EcoRI restriction site, generating two restriction fragments (83 and 52-bp). The T allele removes the restriction site and cannot be cleaved by EcoRI.