The polymorphic regions of leptin and BMP4 genes were amplified by polymerase chain reaction (PCR) with primer sets previously designed by Mórocz et al. [20 (link)]. The PCR was carried out in a reaction mix of 20 μL containing 100 ng DNA and 10x Prime Taq buffer (Genet Bio, Korea), 10 mM dNTPs mixture (Genet Bio, Korea), 20 pmol forward and reverse primers (AlphaDNA, Canada), and 0.1 U Prime Taq DNA polymerase (Genet Bio, Korea). PCR amplifications were performed in an AB 2720 Thermocycler (Life Technologies, USA) with an initial denaturation at 94°C for five minutes and a final extension of seven minutes at 72°C. The following thermal cycle was repeated 30 times: denaturation at 94°C for 30 seconds, annealing at 55°C for leptin and 59°C for BMP4 for 30 seconds, and extension at 72°C for 30 seconds.
The PCR products were cleaved with the restriction enzymes: HhaI (NEB, USA) for leptin and MluCI (NEB, USA) for BMP4, according to the manufacturer's instructions, and the obtained fragments were separated on agarose 3% gel in VG-SYS Horizontal Electrophoresis System (Biochrom, UK).