2.4. DNA extraction
DNA was extracted using Plus Blood Genomic DNA Purification Kit (GeneMark Diagnostics, Carlsbad, CA, USA) according to the manufacturers’ instructions. NanoDrop 2000c spectrophotometer (Thermo Fisher Scientific, Waltham, Massachusetts, USA) was used to measure DNA concentration and purity at 260/280 nm in extraction samples. The extracted DNA was stored at −20°C prior to testing.