An idea to explore: Determination of single nucleotide polymorphisms in alcohol metabolism-related genes using PCR-based assays to understand the link between an individual's genotype and phenotype

Here, we propose a laboratory exercise to quickly determine single nucleotide polymorphisms (SNPs) in human alcohol dehydrogenase 1B (ADH1B) and aldehyde dehydrogenase 2 (ALDH2) genes involved in alcohol metabolism. In this exercise, two different genotyping methods based on polymerase chain reaction (PCR), namely allele-specific (AS) PCR and a PCR-restriction fragment polymorphism (RFLP) analysis, can be performed under the same PCR program (2-step × 35 cycles, 35 min total) in parallel using a hair root lysate as a template. In AS-PCR, the target regions of the G- or A-alleles of both genes are allele-specifically amplified in a single PCR tube. In the PCR-RFLP analysis, the two genes are amplified simultaneously in a single tube, and then a portion of the PCR product is double-digested with restriction enzymes MslI and Eam1104I for 5 min. The resulting reaction products of each method are electrophoresed side by side, and the genotypes are determined from the DNA band patterns. With the optimized protocol, the whole process from template preparation to genotyping can be completed in about 75 min. During PCR, students also perform an ethanol patch test to estimate their ability to metabolize alcohol. This series of experiments can help students learn the principles and applications of PCR/SNP analyses. By comparing the genotypes revealed by PCR and the phenotypes revealed by the patch tests, students can gain a better understanding of the clinical value of genetic testing.