You Must Remember This

et_al at my-deja.com et_al at my-deja.com
Thu Oct 18 23:25:27 EST 2001


On Tue, 16 Oct 2001 19:32:40 +1000, Michael Jameson
<m.jameson at hunterlink.net.au> wrote:

>The New Scientist article indicated that the general hypothesis has 'only
>circumstantial evidence so far' - 'DNA certainly has the capacity to act as a
>stable blueprint...

And its this very point that makes me doubt the theory. DNA *is* fairly
stable, yet this theory proposes to make it less so. Any one neuron may
be involved in the 'storage' of many memories, so the DNA would have to
be subtly modified for each one, which seems fraught with danger to me.
How do you ensure that changes are only made to the "waste" 97%  and not
the "active" 3%  where even a small change could have catastrophic
effects for that cell.

The second problem I can see is that memories are not permanent, cast in
concrete, unchangeable things. My recollection of a past event can, and
often does, change over the years. How does that fit with them being
stored in "a stable blueprint"?  It seems to me this theory changes
memory from, say, the malleability of this post stored on my HDD to the
permanence of it being burnt into a CD and that doesn't seem to accord
with reality.

OTOH, the best theory we have, that storage is a product of the
plasticity inherent in changes to cell interconnections, synaptic
density, receptor types/placement/densities, etc, seems to be consistent
with what occurs in practice. Moreover, we know these changes do occur.

>> And no, more that 3% of the data are used.
>> That would say that only 3% of the DNA were used to create a human during
>> developement.
>> It seems more data are required
>
>I don't understand. The abstract said that 'approximately 3% of our DNA is
>used'. How are 'DNA' and 'data' interchangeable? Do you believe that 3%
>figure to be incorrect?

I don't know whether it is or not, but it seems probable.

Every cell, including neurons, contains the entire DNA sequence needed
to make any of the bodies cells, but a particular cell only needs to
read a small part to function.  So that reduces the "active" percentage
considerably.

And quite a bit of the DNA is "junk" that we and our ancestors right
back to the primordial soup have accumulated from transcription errors,
viruses splicing parts of their DNA into it, charged particle damage,
etc.  

Add that all up and the amount of DNA that controls a particular cell is
probably fairly small, though I'm guessing that all may need to be in
place for the cell to be viable.  I don't think you could have a cell
that only contained just the DNA sequences it needs. Which opens the
possibility that while the cell may not actively use a particular
section, that doesn't necessarily mean it isn't important in finding the
right sections. Perhaps someone who knows more about this could comment.

Ian




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