I'm aligning some mouse RNA-Seq libraries against the genome using STAR. After that, I started to analyse the insert size with Picard. I noticed two types of histogram.
The one showed in Histogram A have a single peak, around 180 bp. The type represented in Histogram B, however, have multiple peaks.
As the aligment was done against the genome, I expected that all libraries would have displayed a pattern like the one in Histogram B, as the spliced inserts would produce "artificial" inserts sizes. So, why did I got these two kinds of histograms?
Thanks a lot!