Every cell holds the same full genome, yet a skin cell and a brain cell look nothing alike — because each keeps different genes switched on or off. Gene regulation is the panel of dimmer switches that decides which instructions a cell actually uses.
Same DNA, different cells
Nearly every cell in an organism carries the same DNA, yet a neuron differs from a muscle cell because they express different genes. Gene regulation controls which genes are transcribed, when, and how much.
In bacteria, an operon groups related genes under one switch (a promoter and operator), so they're turned on or off together — e.g. the lac operon responds to lactose.
- Note that a neuron and a skin cell share the same genome.
- Ask what makes them different.
- Connect the answer to which genes are expressed.
What you should see: Different cells express different subsets of the same genes — that selective expression is gene regulation.