Subject: RE: seashells have dna in them
From: daniel s milling jr <[email-masked]>
To: [email-masked]
Date: Thu, 11 Aug 1994 04:42:59 -0500 (CDT)

This is directed to whoever asked about the DNA helix.  (Sorry I lost
that message...too much mail.)

  If you want to create a very simple double helix.  Just create a couple
of simple spheres (8 sides, 4 segments) with a diameter of say, a meter.
Seperate them by about 2 meters and create a thin rectangular box connecting
the two.  Now create 2 more boxes perpendicular to the first and place them
at the bottom tip of both spheres, one for each.  Now make sure to center
the middle of the first, vertical box on the 0,0 point.  Go to Clone and
set your values to:  #clones = 25 (or whatever you want), offset -2 on Y,
rotation = 10 (or whatever you want) on Y.   You should now get a double
helix.  By changing the rotation you can create a more or less tightly
packed strand.

  Now, if you want to actually show the chemical structure, not just 
a simplistic representation, it will take a bit more work.  One way I could
see doing this is to first model your structures (A, G, C and T) and for each
bond create each single AT or GC bond and place that in another layer with
the original in the first layer.  Calculate the offset on the Y axis (for
example, after the first bond the offset would be -2, for the second -4
and so on.)  Also calculate the rotation on the Y axis (for the second
bond it would be 10 deg. for the third it would be 20 deg etc.)
Use these values to either clone them (after which deleting the original)
or moving and rotating by hand (much easier.)  Once the bond has been 
modified paste it to the layer containing the rest of the chain.

  That's one way to do it.  If you want an example, I whipped up a simple
chain in about 5 minutes.  Leave private email if you want it uuencoded
to you.

Hope this helps.

Dan Milling
[email-masked]