In a bacterium, the malX operon consists of a regulatory gene, malR, and three structural genes: malA, malB, and malC. The malR gene codes for a repressor protein. In the absence of maltose, the repressor binds to the operator region and prevents transcription of malA, malB, and malC. When maltose is present, it binds to the repressor and inactivates it, allowing transcription to occur. In eukaryotes, gene expression is controlled by transcription factors. The plant hormone gibberellin promotes growth by activating genes.
Explain the differences between structural genes and regulatory genes, using the malX operon as an example. Then explain how transcription factors control gene expression in eukaryotes, and how gibberellin activates genes by causing the breakdown of DELLA protein repressors.