Directional/stranded RNA-seq data
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https://chipster.csc.fi/manual/library-type-summary.html

The reads on the left are from the same strand as the transcript, and their pairs on the right are from the opposing strand. The number above the read states which read it is, the first (/1) or the second (/2). Thus, perhaps a bit unintuitively, the first case, "fr-firststrand" is such that the first read (/1) is actually from the opposing strand as the transcript, and second read (/2) is from the transcript strand. -