I see another sequence running under mine. What can cause this?
Some of the causes of another sequence appearing under the primary sequence are:
• Contamination: There is more than one species of DNA present (e.g., multiple PCR products).
• Primers: Primer is annealing in more than one location on the template, primer dimer, primer degradation or not manufactured properly resulting in N+1 or N-1, carry over from PCR reaction, or primers pairs in a multiplex reaction that are not appropriate for multiplexing (i.e., primers anneal inappropriately).
• Spectral/Matrix: If the raw data signal intensity of the sample is too high or saturated it can exceed the amount of color bleedthrough (or spectral overlap) that the matrix (310) or spectral (3130, 3730, 3500) are removing, resulting in secondary peaks appearing in a very specific pattern (e.g., a red peak always appearing under a green peak). A change in the camera, laser, or optical alignment requires that a new matrix be made or a new spectral calibration be performed.
For more information on more than one sequence or set of peaks in a sequencing run, please refer to the DNA Sequencing by Capillary Electrophoresis: Applied Biosystems Chemistry Guide: Second Edition (Cat. No. 4305080, Rev. C). The guide can be found by searching the Thermo Fisher Scientific website with the catalog number 4305080.
Find additional tips, troubleshooting help, and resources within our Capillary Electrophoresis Applications Support Center.
• Contamination: There is more than one species of DNA present (e.g., multiple PCR products).
• Primers: Primer is annealing in more than one location on the template, primer dimer, primer degradation or not manufactured properly resulting in N+1 or N-1, carry over from PCR reaction, or primers pairs in a multiplex reaction that are not appropriate for multiplexing (i.e., primers anneal inappropriately).
• Spectral/Matrix: If the raw data signal intensity of the sample is too high or saturated it can exceed the amount of color bleedthrough (or spectral overlap) that the matrix (310) or spectral (3130, 3730, 3500) are removing, resulting in secondary peaks appearing in a very specific pattern (e.g., a red peak always appearing under a green peak). A change in the camera, laser, or optical alignment requires that a new matrix be made or a new spectral calibration be performed.
For more information on more than one sequence or set of peaks in a sequencing run, please refer to the DNA Sequencing by Capillary Electrophoresis: Applied Biosystems Chemistry Guide: Second Edition (Cat. No. 4305080, Rev. C). The guide can be found by searching the Thermo Fisher Scientific website with the catalog number 4305080.
Find additional tips, troubleshooting help, and resources within our Capillary Electrophoresis Applications Support Center.