'PER' genome-wide base composition bias curves. (a,b) Shown is the GC bias in Illumina reads from a 400-bp fragment library amplified using the standard PCR protocol (Phusion HF, short denaturation) on a fast-ramping thermocycler (red squares), Phusion HF with long denaturation and 2M betaine (black triangles), AccuPrime Taq HiFi with long denaturation and primer extension at 65°C (blue diamonds) or 60°C (purple diamonds). To calculate the observed to expected (unbiased) read coverage, the number of reads aligning to 50-bp windows at a given %GC was divided by the number of 50-bp windows that fall in this %GC category. This value was then normalized relative to the average value from 48% through 52% GC and plotted on a log10 scale (a) or linear scale (b).
Aird et al. Genome Biology 2011 12:R18 doi:10.1186/gb-2011-12-2-r18