In the process of isolating DNA for transcription and translation, you digest the DNA with BamHI ad ligate the gene into a plasmid vector. However, even though all of the controls work, no transcription is obtained using your fragment. Working backward, you note that restriction digestion has removed approximately 250 base pairs from the 5' end of the gene. What is a possible explanation for this observation?

the promoter was removed

Explanation:

Based on the scenario being described within the question it can be said that one possible explanation for this observation is that the promoter was removed. The promoter is a sequence of DNA which protein bind to in order to initiate transcription of a single RNA from the DNA downstream of it. Therefore if the promoter was removed, no transcription would be initiated, such as it happened in this situation.