3 questions involving genes, proteins, and eukaryotic cells!

1) A mutation in the promoter region of a gene prevents recognition by the transcription factors.  Explain the affect this has on transcription and translation.  How could this increase the risk of cancer?

2) Explain the evolutionary significance of introns and exons in eukaryotes.

3) A biologist inserts a genes from a human liver cell into the chromosome of a bacterium.  The bacterium then transcribes and translates the gene.  The protein produced is useless and is found to contain many more amino acids than does the protein made by the eukaryotic cell.  Explain why.

Thank you and only looking for short answers!