Final answer:
Groups of closely related prokaryotic genes controlled by one promoter are organized into operons, such as the LAC operon for lactose metabolism in bacteria. The promoter region binds transcription factors that either initiate or inhibit transcription of the genes in the operon. Eukaryotic gene regulation also involves promoter and transcription factor interactions, but typically on an individual gene basis.
Step-by-step explanation:
Groups of closely related genes coding for enzymes or other proteins that are all controlled by one promoter are organized into operons. In prokaryotic cells, operons allow for efficient regulation of gene expression. The operon model is the most well-known system of this type and includes components such as the promoter, operator, and structural genes. An example of an operon is the LAC operon which is essential for the metabolism of lactose in bacteria. Regulation occurs through proteins that bind to the operon's regulatory region, comprising the promoter and the operator. These proteins, known as transcription factors, can either activate or repress transcription, thereby controlling the synthesis of the proteins encoded by the operon's genes.
The promoter is a DNA sequence located upstream of the coding region, which serves as the binding site for RNA polymerase and transcription factors. The specific interaction between these factors and the promoter initiates or inhibits transcription. In some cases, activators enhance transcription, while in others, repressors can bind to the operator sequence to prevent transcription. This regulatory mechanism ensures that genes are expressed only when needed, conserving cellular resources and responding to environmental changes.
In eukaryotes, the organization of genes differs involving monocistronic mRNA and multiple RNA polymerases, but the core concept of gene regulation by promoter interactions with transcription factors remains similar. Unlike prokaryotic operons which can control the expression of several related genes in one transcript (polycistronic mRNA), eukaryotic genes are typically regulated individually.