Why are the PCR reagents stored on ice at all times?

PCR reagents are stored on ice at all times to preserve the integrity of the samples and reagents and prevent thermal degradation of the proteins and enzymes being studied.

Heat denatures the enzymes causing non-specific annealing and unwanted by-products. This can cause a number of problems including low signal, non-specific signal for the targets, or high background for most of the samples. Storing the reagents on ice at all times helps produce sensitive and consistent results.