Final answer:
Deleting a sequence similar to a TATA box upstream of a gene generally results in decreased transcription of that gene, due to impaired binding of necessary transcription factors and RNA polymerase.
Step-by-step explanation:
If you are deleting a segment with the sequence TATAAG 30 bases upstream of a gene, you might expect that transcription of the gene would be decreased. This is because the sequence you are deleting is similar to a TATA box, a common promoter element found about 25-35 bases upstream of the transcription start site in many genes. This region of the DNA is crucial for the binding of transcription factors and RNA polymerase during the initiation of transcription. Without it, the efficiency of transcription initiation is likely to be impaired, leading to reduced transcription levels of the gene.
As suggested by the reference materials, when mutations occur in the promoter sequence where RNA polymerase binds, RNA polymerase may not be able to attach, leading to decreased transcription levels. Moreover, the binding of transcription factors to enhancer regions typically increases transcription of an adjacent gene, and alterations to such regulatory elements can vastly affect gene expression.