Fig. 2
From: pTrimmer: An efficient tool to trim primers of multiplex deep sequencing data
Two conditions of sequencing read. a The ‘read-through condition’ has a forward primer (5′ end) and a reverse complementary primer (3′ end) at the right and left ends of both read1 and read2. This situation is pretty popular in liquid biopsy studies, where the amplicon length is around 140 bp due to the confine of cfDNA fragment length while the read length could be 150 bp. b The ‘normal condition’ only has forward primer at the 5′ end of reads, both read1 and read2. This occurs when the amplicon length is larger than read length