Services - DNA Sequencing Electropherogram
Figure 9
Electropherogram that has a strong stop.

This sequence is characterized by a rapid decline in signal strength across 5 to 15 bases with the sequence three prime of the region at a significantly lower signal. Presumably this is due to some secondary structure that is inhibiting the modified Taq polymerase in the sequencing reaction kit. The problem is commonly associated with G/C rich or G/T rich regions. The best solution is to sequence the complementary strand if possible. Alternative solutions to this problem include (1) using the dGTP sequencing kit, (2) adding DMSO to the sequencing reaction, (3) raising the annealing temperature, (4) extending the denaturing step, (5) using single stranded DNA or (6) any combination of the above. From experience at this facility in many cases none of these solutions were successful.

A weak stop is characterized by the same rapid drop in signal strength, but the sequence three prime of the stop is still reliable.


 Electropherogram that has a strong stop.