13 ms·

“Study in mice implicates changes to way DNA is organized, regulated rather than changes to genetic code itself” What??

by vrc 4y ago

thaumasiotes 4y ago
The genetic code is the same in every cell, a complete specification of the organism. But cells are highly specialized. For example, you only grow nails on the tips of your fingers and toes. This is due to what your pulled quote characterizes as organizational effects. The level of activity [protein production] of a given stretch of DNA varies wildly from cell to cell. Structural features are attached to the DNA that make it more or less likely to be expressed. What it would produce if it were expressed ("the code itself") doesn't change. For this analogy, you can think of your genome like BusyBox: a single unified executable that will do wildly different things depending on how you call it.
- gausswho 4y ago
  Is it not wasteful for each of our cells to contain genetic code for the whole of the organism? Any particular cell only expresses a tiny subset of that code. Are there any organisms that don't follow this approach? On the other hand, there is a satisfying romance to it all. That a cell is borne and joins into the system ready to grow into anything. It makes our 'self' feel like a co-operative experiment.
  - thaumasiotes 4y ago
    > That a cell is borne and joins into the system ready to grow into anything. That generally doesn't happen; a single-cell fertilized egg will grow into the whole organism, but the more usual birth of cells, from the division of an older already-specialized cell, preserves the older cell's existing epigenetic markings. > Is it not wasteful for each of our cells to contain genetic code for the whole of the organism? Depends on your point of view. From an evolutionary perspective, DNA is the part of you that replicates and so having more copies of it is its own reward.
  - Rury 4y ago
    This is likely an open question. I'm not an expert, but I'd imagine the main reason (at least our) cells all contain genetic code for the whole organism, is largely because stem cells contain genetic code for the whole organism. If stem cells didn't have genetic code for say, both heart cells and lung cells, then it couldn't turn into those types of cells. And since all cells, stem from stem cells... then they also end up with the genetic code for the whole organism. Additionally, DNA is regularly used for creating proteins a cell needs for various purposes. Having extra genetic material than necessary, probably provides some benefits in terms of robustness. Like imaginably when a cell is exposed to a toxic substance, and has genetic code (recipe) for a protein that can neutralize it. Maybe 99% of the time it never needs that genetic code, nor is unnecessary to the cells particular function, but having it around can be beneficial in those rare circumstances. So is it wasteful and bad? Perhaps, but it likely also comes with some positive tradeoffs.
dekhn 4y ago
DNA is "organized" into three dimensional structures which are only partly dependent on the genetic sequence in the region. It's like a rope that's tied up in knots, or twists. Regulation of that structure has huge implications on the accessibility of regions of code, such that regions that are locked inside can't be transcribed into DNA. The management of this complex 3d structure has huge impacts on phenotype, without modifying the code.

“Study in mice implicates changes to way DNA is organized, regulated rather than changes to genetic code itself” What??

by vrc 4y ago

“Study in mice implicates changes to way DNA is organized, regulated rather than changes to genetic code itself” What??

The genetic code is the same in every cell, a complete specification of the organism. But cells are highly specialized. For example, you only grow nails on the tips of your fingers and toes. This is due to what your pulled quote characterizes as organizational effects. The level of activity [protein production] of a given stretch of DNA varies wildly from cell to cell. Structural features are attached to the DNA that make it more or less likely to be expressed. What it would produce if it were expressed ("the code itself") doesn't change. For this analogy, you can think of your genome like BusyBox: a single unified executable that will do wildly different things depending on how you call it.

gausswho 4y ago
Is it not wasteful for each of our cells to contain genetic code for the whole of the organism? Any particular cell only expresses a tiny subset of that code. Are there any organisms that don't follow this approach? On the other hand, there is a satisfying romance to it all. That a cell is borne and joins into the system ready to grow into anything. It makes our 'self' feel like a co-operative experiment.
- thaumasiotes 4y ago
  > That a cell is borne and joins into the system ready to grow into anything. That generally doesn't happen; a single-cell fertilized egg will grow into the whole organism, but the more usual birth of cells, from the division of an older already-specialized cell, preserves the older cell's existing epigenetic markings. > Is it not wasteful for each of our cells to contain genetic code for the whole of the organism? Depends on your point of view. From an evolutionary perspective, DNA is the part of you that replicates and so having more copies of it is its own reward.
- Rury 4y ago
  This is likely an open question. I'm not an expert, but I'd imagine the main reason (at least our) cells all contain genetic code for the whole organism, is largely because stem cells contain genetic code for the whole organism. If stem cells didn't have genetic code for say, both heart cells and lung cells, then it couldn't turn into those types of cells. And since all cells, stem from stem cells... then they also end up with the genetic code for the whole organism. Additionally, DNA is regularly used for creating proteins a cell needs for various purposes. Having extra genetic material than necessary, probably provides some benefits in terms of robustness. Like imaginably when a cell is exposed to a toxic substance, and has genetic code (recipe) for a protein that can neutralize it. Maybe 99% of the time it never needs that genetic code, nor is unnecessary to the cells particular function, but having it around can be beneficial in those rare circumstances. So is it wasteful and bad? Perhaps, but it likely also comes with some positive tradeoffs.

dekhn 4y ago

DNA is "organized" into three dimensional structures which are only partly dependent on the genetic sequence in the region. It's like a rope that's tied up in knots, or twists. Regulation of that structure has huge implications on the accessibility of regions of code, such that regions that are locked inside can't be transcribed into DNA. The management of this complex 3d structure has huge impacts on phenotype, without modifying the code.