Eli5: How do bones and other organs know what shapes to grown into?
In: 3675
I use building analogies with my niece and nephew to describe ‘developmental biology’, since they live in houses and know most of the everyday items.
When you build a house, you start with a piles of bricks, piles of wood, tiles, and the like. You could build lots of different houses (body plans in our analogy) from those same materials, so you need a house blueprint to tell you how to put everything together (which inside us is our DNA).
When you start “building” it’s very simple, just a roof, walls, and basement if your type of house has them (this is like the skin, skeleton, and muscles in us) – and at the beginning its still pretty easy to make changes, very little is locked in. Once you’ve laid out the area for the kitchen, bathrooms, bedrooms, etc, then you start on the more intricate parts. Air-conditioning vents are like the vascular system, outlets and wiring are like the nervous system, and piping is like the digestive system. By this point it’s harder to make big changes. You might be able to move a sink from one part of the bathroom to another, but moving the kitchen to the other side of the house is going to be impossible.
The important part of the analogy is the blueprint doesn’t build the house, just like our DNA doesn’t build us. It’s just the instructions followed by the workers (proteins and transcription factors). Some parts of the blueprints are specified in exact detail (the door goes here!), other parts are up to the workers on some level (the floor is hardwood, now build it, I’m not telling you exactly where to cut each single piece of wood but here’s a rule about how they align).
For a eli5 discussion and without going into all the painful details – just know all the worker rules and instructions aren’t known yet (how we get from blueprint to structure) and that’s what biologists are working so hard to figure out.
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