| Nah, you can consider puberty to be a less extreme form of metamorphasis. Hundreds of genes are switched on and off to accomplish rather drastic sexual and physical changes. Switching genes is cheap and easy. You have dozens of genes that switch on/off acting as pacemakers and timers. You have other genes that switch on when there is a boost of insulin, and then turn back off once the insulin is gone. There are genes that are only turned on when stressed, hypoxic, over-temperature, under-temperature, over-fed, underfed, growing, not growing, genes that turn on when neurons are excited or inhibited. The list is endless. If you think of your body as one giant state machine, it makes sense that you need thousands of flags to control the exact state that it is in. It's actually much more complicated, since genes really aren't binary. Each gene is also a scalar, producing varying quantities of protein, or causing various kinks in the DNA which affects nearby genes (called "enhancers"). So really, you have a bunch of binary states which are then modulated by the amount of protein that is being created. Then you have different parts of a gene that can be individually turned on/off, producing different isoforms of a single protein. Each isoform has different capabilities, especially when paired with regulatory proteins that modulate it's behavior (which also have their own regulation at the genetic and proteomic level). And each of these proteins in turn effects an numerable array of other proteins and genes, cascading throughout the entire system. The body is a remarkably vast state machine. Edit: This is totally ignoring all the microRNA and shRNA which modulates the state between DNA translation and transcription. Basically, add a few more million states to the state machine. |