Schematic representation of the experimental design.

<p>(A) 20 sgRNAs were inserted into 20 sgRNA backbones with distinct barcodes by Golden Gate assembly. Then the samples were pooled at different steps of the procedure and sequencing libraries were constructed from either plasmids or genomic DNA extracts of infected K562 cells (see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0198635#sec002" target="_blank">Methods</a>). In total, we constructed two libraries from plasmids and four from the genomic DNA samples. (B) Schematic representation of the library construction procedure.