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I always wonder why they need a scaffold. Isn't the programming for the shape of the bone programmed into the DNA?

If for some reason we can't access that programming, how do we tell the cells "divide anywhere you want until you fill up the scaffold"? It seems like that's something they wouldn't naturally do.

I guess long term, we should find the point in fetal development where the first jaw bone cell becomes differentiated. Then we want to to tell a single stem cell "that's you, you're that first differentiated fetal jaw cell, now do your thing".

What do you guys think? Is anyone working on that?

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Cell growth isn't independent of the cells around them.

For example if you get cut the cells around a gap will send out external signals (send and pray) which might cause other cells to start growing. Once the gap is filled (i.e. the cells are adjacent to each other) the surrounding cells will again send out signals to tell them "Stop! Space is getting tight!".

Sometimes its also the other way (or a combination of both) and a cell will detect an empty area and grow.

Here's a link to a game to show how cell growth works: http://nobelprize.org/educational_games/medicine/2001/cellcy...

I guess we need to start with the first cell, and then simulate the existence of the correct cells around it. A machine that produces the right chemicals at the right times and places.

It does not work the way you think it does. Cells signal other cells and structures form in part based on chemical gradients. This is why animals born with extra limbs can still control them and each cell used to form a bone reacts based on the other cells around it. Consider how the body needs to supply blood the the bone marrow. Blood is entering your jawbone and exiting in separate areas. A network of capillary's deep within the bone in an unbroken chains back to your heart.

Random observation. "Can still control them" and "Can usefully control them" are two different things. For instance there is a genetic disorder where people are born with 6 fingers on each hand. However you still only have nerves to your brain for 5 fingers, and the last finger is just a copy of your little finger. You literally can't do anything with the one without doing the same thing with the other.

That was more detail than people probably wanted to know.

I thought it was fine actually.

Wasn't that at some point quite a frequent occurrence in South America ?

If I recall correctly, wasn't the sixth finger actually a dominant trait?

There are multiple genetic disorders that can cause 6 fingers. Several, but not all are a dominant trait.

I don't know whether it was ever common in South America. However http://en.wikipedia.org/wiki/Polydactyly says that it is much more common in blacks than whites.

1 in 500 ? That's a whole lot higher than I would expect!

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