On 8/4/2011 6:02 AM, Invisible wrote:
> On 04/08/2011 01:53 PM, Le_Forgeron wrote:
>> It's even worse than that: each customer not only get a full different
>> program, but installed it (with variations) on billions of computers
>> (most cells get a full copy, initially).
>>
>> As cells divide, each copy mutates and get truncated or duplicated code.
>> Statically, it's the same program... in theory. In practice, the
>> survival is only based on the ability of the new program to still
>> duplicate the cell.
>
> As best as I can tell, mutations are actually very rare events. There
> are specific mechanisms which exist expressly to detect and correct such
> defects. That includes DNA repair mechanisms, automated destruction of
> misfolded proteins, and extracellular signals used to program mutated
> cells to shut down and die.
>
> Cancer happens when these mechanisms fail to correct a mutation /and/
> that mutation happens to be do to with growth processes. Observe that
> cancer is quite rare. (E.g., it's not like 50% of people get cancer or
> anything like that.)
>
> So it's not like every single cell in your body has a completely
> different copy of your genome. Actually the differences are tiny, if
> existent at all. The major place where these mutations become
> significant is during reproduction, where the entire organism passes
> through a single genome copy. If /that/ gets changed, it's probably
> permanent.
You are assuming that all of the code is run, in all copies. That isn't 
true though. To use your program analogy, every copy may have accounting 
functions, but only 10 of the customers are using it. Or, worse, the 
"code" that gets mangled is in the initialization code, so it effects 
each "new" unit that goes online, but the machine someone accidentally 
enclosed behind a wall, and has thus been running for years as a server, 
isn't effected, since it never has to run the initial code that does the 
first "setup", it simply reads that data in again, when/if it has to 
restart. Like a liver cell that produces liver cells fine, but has major 
errors in code related to forming something else specific, like lungs, 
or something general, like initial signaling that determines symmetry in 
the organism. Neither of which is needed, in a liver cell.

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