1：Replace the experimental supplies in time

Set up (NTC) negative control and repeat it many times. Once it is found that there is PCR product contamination in the laboratory, replace all experimental supplies in time. Such as: re-dilute and prepare the primers, re-sterilize the pipette tip, EP tube, ddH2O, etc., replace with a new pipette, and temporarily borrow other laboratories to perform PCR experiments. The contaminated laboratory shall be ventilated and irradiated with ultraviolet rays until the PCR product contamination is eliminated before proceeding with the experiment.

2：Extend UV exposure time

It is worth noting that to remove DNA contamination, regular ultraviolet radiation should be extended by 2 hours than usual. Even so, the effect of UV irradiation on removing small fragments (below 200bp) of DNA contamination is still not good.

Ultraviolet wavelength (nm) is generally 254/300nm, and it is enough to irradiate for 30 minutes. It should be noted that when choosing UV to eliminate the contamination of residual PCR products, the length of the PCR product and the distribution of bases in the product sequence should be considered. UV irradiation is only effective for long fragments above 500 bp, and has little effect on short fragments.

During UV irradiation, the pyrimidine bases in the PCR product will form dimers. These dimers can terminate the extension, but not all pyrimidines in the DNA chain can form dimers, and UV irradiation can also break the dimers. . The degree of dimer formation depends on the UV wavelength, the type of pyrimidine dimer and the sequence of nucleotides adjacent to the dimer site. Therefore, if the PCR amplified fragments are small, it is recommended to use the UNG anti-PCR product contamination system.

3：Commonly used DNA pollution scavengers

Aerosols are easily generated when pipettes are added, which is difficult to avoid, and it will settle quickly. Therefore, it is undoubtedly a good choice to frequently use special DNA pollution scavengers to prevent the spread of DNA pollution.

4：Use UNG anti-pollution system

After the PCR product contamination is removed, the testing laboratory can use the UNG anti-PCR product contamination system to prevent PCR product contamination. In general laboratories, you can perform simple experimental partitions, strictly separate the PCR product area from other areas, establish certain laboratory rules and regulations, and conduct relevant training to prevent the occurrence of PCR product contamination.

Recommendations: Establishing a reasonable PCR laboratory, maintaining a good PCR environment, formulating standard PCR operating procedures, and cultivating the rigorous operating awareness of experimenters are the keys to preventing or reducing the pollution of PCR experiments.