Why 5'-3' and not 3'-5'

Fri Mar 27 08:38:37 EST 1998

In reply to Adams quip about evolutionaRy design and why the phosphate 
doesn't hang off of the 3' carbon, I'm sure an answer could be found 
in the thermodynamics of nucleotide synthesis, but perhaps a second 
answer might be in the geometry of nucleic acids.  The way DNA is 
designed, the bond angles allow for the formation of a double helix 
with relatively tight turns, and exquisite symmetry.  This may allow 
for efficient packaging of large pieces of nucleic acid inside very 
tight spaces.  Try drawing a double helix with the phosphate on the 3' 
carbon, and see what you get.

Jay Mone

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