There is a tailing phenomenon in electrophoresis, and English becomes smear, which means diffusion. The reasons are mainly considered from the following two aspects:

1, PCR products themselves:

Too many non-specific products of PCR are often caused by too much enzyme or poor enzyme quality, too high dNTP concentration, too high Mg2+ concentration, too low annealing temperature and too many cycles.

Countermeasures: ① reduce the amount of Taq enzyme, or change the enzyme from another source; ② reduce the concentration of dNTP; ③ appropriately reduce the concentration of Mg2+; ④ increase the amount of template, reduce the amount of primer, reduce the number of cycles and increase the annealing temperature.

2. Problems of electrophoresis system:

(1) The electrophoresis buffer TAE or TBE is polluted, so it is recommended to replace the buffer. (2) The sample is floated when loading, so it is recommended to increase the loading buffer and add the sample carefully. (3) The voltage is too high. (4) Increase the concentration of your gel appropriately. (Depending on the size of your fragment) (5) Observe whether there is tailing phenomenon in your marker.

Many people have asked this question before, and borrow the best answer to the previous question.