Size selection of the Nextera DNA libraries by agarose gel size selection. (A) Electropherogram of DNA library analyzed by 2100 Bioanalyzer. The library size of the Nextera DNA Sample Prep Kits was 150 bp to more than 10 kb (mean size: 902 bp). (B) Bioanalyzer electropherogram of a selected DNA library by cutting from the agarose gel. We selected large fragments with sizes ranging from 500 to 2,000 bp to remove short DNA fragments for effective HLA gene haplotype phasing. The size selection also determines an actual molar concentration for bridge PCR to generate clusters in flowcell, because DNA fragments with over 1.5 kb size are not efficiently amplified. The mean size of the selected fragments was 1,561 bp.