2.3 DNA extraction, Library construction and sequencing
DNA was extracted from available blocks with the TIANamp Micro DNA Kit (DP316, Tiangen Biotech) following the manufacturer’s protocol. We constructed DNA libraries according to the standard protocol through end-repaired adapter added overnight, and by applying polymerase chain reaction amplification to the extracted DNA. To measure the adapters before sequencing, quality control was carried out using a bioanalyzer (Agilent 2100, Ag­ilent Technologies, Santa Clara, CA, USA) combined with quantitative PCR. DNA se­quencing was then performed with the BGISEQ-100 plat­form.