4 ms·

Ok, are those chemical gradients encoded in DNA?

sn9 4y ago
They're encoded in the laws of physics. Kinda like asking if gravity and fluid dynamics are encoded in the blueprint for an aircraft. The design relies on them, and exists in the form it does because of them.
- throwaway4aday 4y ago
  I don't think the blueprint analogy works here. From what I know, DNA doesn't have any set blueprint for the positions of all of the cells in the body. It encodes for molecules that form cells and then the cells somehow self-organize into structures that eventually form the complete body. To me, using a blueprint analogy you'd have to say the blueprint describes an airplane that once you construct enough of them interact in such a way as to build their own airports, plan their own routes, fly themselves and produce their own online booking software and that's still nowhere near as complex as what's happening inside a nematode let alone a human.
  - sn9 4y ago
    Yeah that's a little more accurate. Analogies are usually limited. But though it's not literally about locations in the sense of physical coordinates, the way cell signalling and the molecular feedback loops that drive development are still reliant on basic physical laws. It would be completely redundant and unnecessary to encode those laws themselves since they're invariant across time and space. Physics and chemistry are fixed. It would never make sense for DNA to literally encode information about physical laws in the same way it wouldn't make sense to do so on an airplane blueprint, because the design of the blueprint was itself constrained by those laws, as would any alternative design.
Balgair 4y ago
Short answer: No. Medium answer: Kinda. The chemical gradients cause a signaling cascade that modifies transcription of DNA (it's really complicated). This transcription change then causes the cell to become a XXX_neuron. However, there are many many waves of this process occurring with a lot of cell death along the way. When those cells are not the 'final' cell of the nervous system, these transcriptions can cause further and more complicated chemical gradients to exist in the fetus. These complicating recursive loops can also self-affect cells and cause them to change yet again. We're still discovering a lot here. Also, this is largely how ALL cells in a body work, not just neurons. Be careful though, this is very very complicated stuff and everything I've written has a caveat.

sn9 4y ago

They're encoded in the laws of physics. Kinda like asking if gravity and fluid dynamics are encoded in the blueprint for an aircraft. The design relies on them, and exists in the form it does because of them.

throwaway4aday 4y ago
I don't think the blueprint analogy works here. From what I know, DNA doesn't have any set blueprint for the positions of all of the cells in the body. It encodes for molecules that form cells and then the cells somehow self-organize into structures that eventually form the complete body. To me, using a blueprint analogy you'd have to say the blueprint describes an airplane that once you construct enough of them interact in such a way as to build their own airports, plan their own routes, fly themselves and produce their own online booking software and that's still nowhere near as complex as what's happening inside a nematode let alone a human.
- sn9 4y ago
  Yeah that's a little more accurate. Analogies are usually limited. But though it's not literally about locations in the sense of physical coordinates, the way cell signalling and the molecular feedback loops that drive development are still reliant on basic physical laws. It would be completely redundant and unnecessary to encode those laws themselves since they're invariant across time and space. Physics and chemistry are fixed. It would never make sense for DNA to literally encode information about physical laws in the same way it wouldn't make sense to do so on an airplane blueprint, because the design of the blueprint was itself constrained by those laws, as would any alternative design.

Balgair 4y ago

Short answer: No. Medium answer: Kinda. The chemical gradients cause a signaling cascade that modifies transcription of DNA (it's really complicated). This transcription change then causes the cell to become a XXX_neuron. However, there are many many waves of this process occurring with a lot of cell death along the way. When those cells are not the 'final' cell of the nervous system, these transcriptions can cause further and more complicated chemical gradients to exist in the fetus. These complicating recursive loops can also self-affect cells and cause them to change yet again. We're still discovering a lot here. Also, this is largely how ALL cells in a body work, not just neurons. Be careful though, this is very very complicated stuff and everything I've written has a caveat.