Mysteries of 'molecular machines' revealedBiological complexity is still not understood. For example, the detection/destruction of foreign DNA is a preemptive measure, not a prescriptive measure. Further the implementation requires two separate entities which communicate with each other.
"Molecular machines that have recently been seen in three-dimensional detail include a "huge" molecular machine called Cascade that was reported in the journal Science this summer. The Cascade machine is present in bacteria and can recognize DNA that comes from viruses that infect the bacteria. The Cascade machine is made up of 11 proteins and an RNA molecule and looks like a seahorse, with the RNA molecule winding through the whole "body" of the seahorse. If a foreign piece of DNA in the bacterial cell is complementary to part of the RNA molecule then another specialized machine can come by and chop up the foreign DNA, saving the bacterium from infection.
Los Alamos and Cambridge University scientists who were developing the Phenix software were part of the team that visualized this protein machine for the first time. The Phenix software has been used to determine the three-dimensional shapes of over 15,000 different protein machines and has been cited by over 5000 scientific publications."
If the communication were not correct, the result could be the destruction of the cell's own DNA - i.e. suicide. Or at least the result would not be the intended action of destroying the invader. So the development and implementation of this feature had to be correct the first time, with no errors, plus it could not be known to actually work until a foreign DNA actually invaded, which lets out evolution.
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