Combine SYBR Green I and dsDNA fluorescence signal can strengthen 800-1000 times. In the polymerase chain reaction (PCR) system, add too much SYBR Green I fluorescent dye,
After SYBR fluorescent dyes mixed specifically the DNA double chain , Fluorescent signal increases. Molecular which not mixed with the chain SYBR Green I dye fluorescent unchanged, In order to ensure that the increase of the fluorescent signal with the increase of PCR products completely in sync. Fluorescence in annealing phase or extensions stage can be determined.