Hey future biologists! 🌿 Ever wonder how your body knows to crank up the heat when it's cold, or why some bacteria decide to munch on sugar only when it's available? Say hello to gene expression, the party planner of the cell world! 🎉

Key Points

• Gene expression can be ON or OFF based on environmental factors.
• In E. coli, genes for lactose metabolism turn ON only when lactose is around.
• Negative Feedback: Repressor protein stops gene expression when lactose is gone.

Real-World Example

Think of E. coli as a smart shopper who loves lactose (milk sugar). Imagine walking into a grocery store (the environment) that has a 'Buy One, Get One Free' sale on milk. Wouldn't you stock up? E. coli does the same: when lactose is available, it activates genes to absorb and metabolize lactose.

Key Points

• In eukaryotes (that's us and plants), only a fraction of genes are expressed.
• Cellular Differentiation: Specific genes are turned on or off to make different cell types.
• Critical in development and life cycles, like a caterpillar becoming a butterfly.

Real-World Example

It's like each cell having a specific job at a music festival. The ticket-checking cell only needs the "Check Tickets" gene on, while the stage-setup cell needs different genes like "Carry Heavy Stuff." They're all part of the same event but need different 'skills' (genes).