Gene regulation is a process in which a cell determines which genes it will express and when. There are a number of reasons why organisms from unicellular animals to blue whales engage in this process, and the regulation of genes is a topic of interest for some researchers who are interested in learning more about how the process works and what happens when it goes wrong.
One of the easiest ways to illustrate gene regulation is to talk about it in humans. Every cell in the human body contains a complete copy of that person's DNA, with tens of thousands of potentially viable genes. All of these genes cannot be expressed at once, so cells must decide which genes to turn on and which genes to turn off. For example, a skin cell turns on the genes that make it a skin cell, while a bone cell would leave these genes turned off. Neither of these cells would need the genes that allow a cell to differentiate into a neuron, so these genes would be left off as well.
In addition to being useful for cell differentiation, gene regulation is also valuable for cell function. As a cell moves through its life, it has different needs and functions, which can be addressed with the use of this process to determine which genes are expressed and when. Likewise, cells can adapt to environmental changes, such as an injury which requires repair by activating new genes. For the cell, gene regulation can be accomplished in a number of different ways, with one of the most common simply being regulation of the rate at which RNA transcription occurs. Genes can also be deactivated by changing the structure of the DNA in an individual cell to turn them off or on.
Unicellular organisms also use this process to regulate their functions and activity. These organisms must be able to adapt genetic material quickly to adjust to changing circumstances and new environments, since the failure to do so will cause not only death of the cell, but death of the organism itself. Gene regulation allows such organisms to do things that will allow them to fit into hostile and extreme environments and to adapt to changes, such as the introduction of antibiotics into their environment.
There are potential therapeutic applications for the process as well. By knowing which genes are involved in a cancer or genetic condition, for example, it is theoretically possible to turn these genes off so that they cannot be active in the body.