Bio-Rad dNTP mix remains stable after precycling. dNTP mix was precycled for 25 rounds of thermal cycling, then incubated with additional reaction components for 25 cycles of PCR. Genomic DNA template (20 ng) was amplified with iTaq™ DNA polymerase using primers to the HFE gene. Two products, one 500 bp and the other 2 kb in length, were both produced in similar amounts regardless of whether the dNTPs were precycled (lanes 2 and 4) or not (lanes 1 and 3). Lane M, 500 bp EZ Load™ molecular ruler.