No. We have not seen the PreCR Repair Mix have a negative effect on a PCR reaction. Because of the complexity of DNA damage there may be cases that we have not encountered in which PreCR treatment has a negative effect. A possible scenario for this would be a situation in which the degraded DNA is mostly single stranded. Some of the repair enzymes can act upon ssDNA, but the ssDNA lacks the complimentary strand required for full repair.