The parts of the DNA molecule doing the chemistry are the same for each
nucleotide, no matter what the base (adenine, cytosine, guanine, or
thymine) is. There may be a very small difference associated with the
electron-withdrawing properties of the base, but I imagine that this would
be negligible. For those who don't already know and might care, the
chemical "numbering" for a DNA molecule (or RNA for that matter) is based
on the purine or pyrimidine base. This base is attached to the 1'
position of the deoxyribose (DNA) or ribose ring. Position 2' of the ring
has an OH group in ribose but this is absent in deoxyribose. Position 3'
of the ring is a derivitized OH group bound to a phosphate which is
attached to the OH group of the 5' carbon below it. Carbon 4' is a member
of the ring and bound to the O of the ring (which is also bound to carbon
1'.
I
-O-P=O
I
O
I
HCH(5') BASE
I I
(4')HC------O------CH(1')
\ /
\ H/
CH(3')--CH(2')
I
O
I
O-P=O
I
O
I
(attached to 5' carbon of the next nucleotide)
Synthesis of DNA in cells takes place in the 5' to 3' direction.
Bill's point is well taken...the probability of the reaction (in terms of
its rating of energy) would definitely affect your product. Proteins are
similar to DNA in that the part of the molecules coupling is the same for
each amino acid. Lipids use different components, though. What astounds
me about origin of life scenarios is how the DNA (or RNA) not only
"learned" to code for the proteins, but that proteins "learned" to build
lipids and then the DNA "learned" to code for those lipid-building
proteins. You can't have a very nice cell without lipids, proteins and
nucleic acids. And they've all got to get themselves into the genetic
code somehow (except for the nucleic acids, since they are the code, but
even those need to find the proteins that can extend them and repair them
and get those into the record). I know I'm being hopelessly
anthropomorphic here, but the subject is hard to write about easily
without being so.
Gene
PS. Of course, I know God did it, but I'd like to see His cookbook. :-)
____________________________________________________________
Gene D. Godbold, Ph.D. Lab: 804 924-5167
Research Associate Desk: 804 243-2764
Div. Infectious Disease Home: 804 973-6913
Dept. Internal Medicine Fax: 804 924-7500
MR4 Bldg, Room 2115 email: anselm@virginia.edu
300 Park Place
Charlottesville, VA 22908
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