Final answer:
To determine which deletion impacts gene transcription and potentially affects an enhancer, observe the changes in transcription levels after each deletion; the one with significant changes likely indicates the presence of an enhancer.
Step-by-step explanation:
When evaluating the level of transcription by creating deletions in a gene, if the transcription level changes significantly, this suggests that the deletion has impacted a regulatory region such as an enhancer. An enhancer is a sequence of DNA that can increase the transcription of genes. Therefore, the deletion that results in a change in transcription level indicates the presence of an enhancer. In this case, suppose deletion 2 resulted in low transcription levels (+), then this would suggest that deletion 2 is in an enhancer involved in regulating the gene.