*2.3. Determination of Genotypes*

The blood samples of 3 mL, obtained from individuals participating in this study, were used for genotyping. The blood samples were centrifuged for 10 min at 1000 × *g*, and deoxyribonucleic acid (DNA) was extracted from the leukocyte layer using a Wizard Genomic DNA purification kit (Promega Co., Madison, WI, USA). The extracted DNA was dissolved in 100 µL of DNA hydration solution and stored at −70 ◦C until analysis. In order to amplify a portion of gene containing a SNP by polymerase chain reaction (PCR) from the extracted DNA, each primer was prepared according to the variation of allele. Moreover, the genotypes were determined using appropriate methods that have been reported in the past [5,8,10,11]. We conducted experiments three times to acquire exact genotype data.
