The document discusses gene regulation and expression in prokaryotes and eukaryotes. In prokaryotes like bacteria, genes are organized into operons and regulated by DNA-binding proteins that control transcription. The lac operon in E. coli regulates genes needed to break down lactose and is turned on or off by the lac repressor binding in the presence or absence of lactose. In eukaryotes, gene expression is more complex and regulated by transcription factors binding regulatory regions and controlling transcription. RNA interference is another mechanism where small RNAs regulate genes by interfering with mRNA. Master control genes regulate development by controlling gene expression and cell differentiation.

1. Lesson Overview 13.4 Gene Regulation and Expression