Optimized PCR conditions rescue GC-rich promoter regions in the human genome. (a,b) A 180-bp fragment library of human DNA was amplified using (a) standard conditions (Phusion HF, short denaturation) or (b) optimized conditions (AccuPrime HiFi, long denaturation, extension at 65°C) on the fast-ramping thermocycler 1. The amplified libraries were analyzed by qPCR. Orange bars indicate the quantity of eight GC-rich loci near gene promoters relative to the mean quantity of four size-matched control loci (blue bars; mean set to 100% in each graph). Error bars represent the range of two measurements averaged to calculate the quantity of each locus. Locus 7 is the first protein-coding exon of the tumor suppressor gene RB1.