>>We are using dye terminator chemistry on the ABI Prism 3700.
>The "G" blob is the only one we are seeing - no "A," "T," or "C" - so,
>we're certain our purification method isn't to blame.
>Any other suggestions would be great.
What method are you using for clean up? This sounds like the results of Ethanol
Precipitation of your sequencing reactions. Typically with this method you will
see only 1 color later in the electropherogram. We typically see either a G
peak or a T peak depending on the chemistry.
DNA Seq Core Facility at Caltech