4.3. Genotyping

DNA samples from POI patients and controls were extracted using the G-DEX blood extraction kit (iNtRON Biotechnology Inc., Seongnam, Korea). miRNA SNPs were selected using the human genome SNP database (dbSNP; http://www.ncbi.nlm.nih.gov/snp): miR-938G>A (rs12416605). Samples were genotyped by PCR-restriction fragment length polymorphism (PCR-RFLP) analysis with the following primers and PCR conditions. miR-938G>A polymorphism was detected using primers (forward) 5′-T GGT GCA CTG GGT TCA CCT TTA AGC G-3′ and (reverse) 5′-GTA ATA CCT CTG AGC CTT TGG GGC C-3′ under conditions of initial denaturation at 95 °C for 5 min; 35 cycles of denaturation at 95 °C for 30 s, annealing at 64 °C for 30 s, and extension at 72 °C for 30 s; and final extension at 72 °C for 5 min. PCR products were digested using the restriction enzyme HhaI (New England BioLabs, Ipswich, MA, USA).