Noninvasive genotyping of dopamine receptor D4 (DRD4) using nanograms of DNA from substance-dependent patients

A noninvasive DNA sampling method has been implemented collecting buccal mucosa cells by cotton wool swabs. An amount of 0.2-2 mug DNA per patient was obtained after the phenol-extraction procedure and 0.2-2 ng DNA template was sufficient for PCR amplification of the polymorphic 48 basepair repeat region of dopamine receptor D4 (DRD4) gene. PCR products were visualized during microfabricated electrophoretic separation by laser-induced fluorescent detection and automatic data registration. Initial data of genotyping drug-dependent subjects shows a relatively high ratio of heterozygotes, possessing either longer or shorter variants beside the common 4-repeat DRD4 allele.