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Denis Alexander is a molecular biologist and it is to the molecular basis of life that he turns in Chapter 3 of his book “Is There Purpose in Biology?” As a chemist, I find this chapter fascinating. Biology is nothing without chemistry. To set the stage: in chapter 1 Denis introduced a historical perspective on the discussion of purpose in biology, in chapter 2 he outlined the Grand Narrative of biology. The increase in complexity in undeniable, from early single-cell organisms to the biodiversity that characterizes life today. The development of this biodiversity is characterized by convergence. Similar structures developed from very different directions. The eye provides one well known example of such convergence. Evolution is not a random process operating in a flat landscape. Rather there are physical constraints and optimal solutions.
There are chemical constraints as well. The cell is a complex bag of chemicals with proteins providing structure, transporting molecules, generating signals, sensing stimuli, and catalyzing critical chemical reactions. These proteins are composed of various arrangements of 20 common amino acids (although chemical modification can provide some additional variation exploited in the cell) along with various metals and other cofactors. The self-replicating DNA chains found in the chromosomes store the information that allows the production of the various proteins and other biological molecules required for life. Four nucleobases labeled A, C, T, and G are arranged in triplets code for the common amino acids. These are paired via hydrogen bonds in the well known double helix of DNA (Image credit).
Stephen - Meyer - Signature - Cell - Specificity
Stephen Meyer (Signature in the Cell) suggested that the specificity of the DNA code was evidence for an intelligent designer. Denis does not refer directly to Meyer’s book, but offers a counterpoint to this argument. Although it is possible that the specific genetic code used by life on earth...
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