FAQ: What are the main causes of blunting reaction failure using T4 DNA Polymerase?

The following conditions can cause the exonuclease to overwhelm the polymerase activity causing recessed instead of blunt ends:
*Adding too much enzyme
*Incubating for too long
*Incubating at greater than 12°C
*Failure to add nucleotides or the nucleotide level is too low
*Heat inactivating without EDTA