MCB 150 Lecture 33: Regulation in Bacteria and Eukaryotes

Flashcards covering key vocabulary and concepts from MCB 150 Lecture 33, focusing on gene regulation in bacteria and eukaryotes.

mRNA Stability in Bacteria

Bacterial mRNAs are short-lived (half-life of approximately 2 minutes), allowing for quick adaptation to environmental changes. The degradation of lac mRNA from the 3′ end influences the ratio of protein products, showcasing the dynamic nature of gene expression in bacteria.

Translation Initiation: Shine-Dalgarno Sequence

The Shine-Dalgarno sequence's strength determines the efficiency of translation initiation, affecting the amount of protein produced. Its availability for ribosome binding can be modulated by regulatory proteins or mRNA secondary structures, adding layers of control to gene expression.

Inducible Operon

An operon whose expression is induced by the presence of a specific substance. The lac operon, responsible for lactose metabolism in E. coli, is a prime example; it is activated in the presence of lactose, enabling the bacteria to utilize lactose as an energy source.

Repressible Operon

An operon is typically active but can be repressed when the end product is abundant. The tryptophan (trp) operon, involved in tryptophan synthesis, is a classic example; it is switched off when tryptophan levels are high, preventing overproduction.

Allosteric Regulation/Feedback Inhibition

The regulation of proteins through allosteric mechanisms or feedback inhibition, exemplified by PFK regulation in glycolysis, allows for precise control over protein activity. This ensures metabolic pathways are responsive to cellular needs and conditions.

Transcriptional Level Regulation

Regulation at the transcriptional level is the most energy-efficient strategy for controlling protein production. By modulating mRNA synthesis, cells can conserve resources and prevent the unnecessary production of proteins that are not immediately required.

Post-Translational Level Regulation

Post-translational modifications and regulations offer a rapid means of controlling protein activity. These mechanisms enable cells to quickly respond to environmental changes or internal signals without altering gene expression.