size of gene insert vs. predicted size - (Mar/02/2009 )

I performed a double digestion using BamH1 and HindIII on a strain of E. Coli. accorrding to the protein sequnce, the size of the insert should be 82 bp. But after the double digestion and looking at it on my agarose gel, I calculated that the insert was 0.745 kb. This is a really big difference....what went wrong here?

Where to start. Did you mean you digested cells, or DNA from cells, or plasmid DNA from those cells? The protein sequence won't tell you where a restriction digest will cut. So, did you really mean a nucleotide sequence? Perhaps you could tell us what you are trying to do.