Read cover of sample junction. A read cover profile shows the number of read alignments (y-axis) that start at a particular distance (x-axis) from the splice junction. This histogram is a typical example of the 50nt neighborhood around a highly expressed constitutive junction. This example exhibits two types of read mapping bias: sparse coverage (empty positions) and read-stacks (tall blue bars). The horizontal line (in red) α = 3.4 marks the average expression of the junction determined by the Native model.