Inheritance: describe question

A plant gene that codes for an enzyme involved in cell elongation is regulated by the hormone gibberellin. The transcription factor that activates this gene is normally kept inactive by binding to a DELLA protein. Gibberellin causes the breakdown of the DELLA protein, freeing the transcription factor to promote transcription. Describe the roles of structural genes and regulatory genes in the control of gene expression, using this example and the lac operon in E. coli. Explain how the transcription factor increases the rate of transcription of its target gene.