Chapter 10 — The Code

DNA is not a machine. It is information—a four-character digital code encoding the construction instructions for every protein in every living system. The four characters are the nucleotide bases adenine, thymine, cytosine, and guanine. In the human genome approximately 3 billion base pairs encode roughly 20,000 protein-coding genes plus an enormous regulatory apparatus. The information density of DNA exceeds any human-engineered storage medium by orders of magnitude.

The critical point is logical, not chemical. Information is not a physical substance. A book is not its paper. A program is not the electrons on the drive. The information in DNA is not in the atoms of the sugar-phosphate backbone—it is in the sequence of the four bases. That sequence is not determined by the chemical properties of the bases. Any base can follow any other base without chemical constraint. The sequence is freely specifiable. That is precisely why it can carry information. And that is precisely why the origin of the sequence cannot be explained by chemistry.

Physicist Hubert Yockey applied Shannon information theory to biological systems and concluded that the information content of the simplest functional protein exceeds what undirected chemistry could produce. We have never observed specified functional information spontaneously arising from non-information anywhere, at any timescale, under any conditions. The appearance of information consistently and without exception corresponds to the activity of a mind. The question is not how chemistry produced the sequence. The question is where the sequence came from.

Yockey, H.P. Information Theory, Evolution, and the Origin of Life. Cambridge University Press, 2005. Watson, J.D. and Crick, F.H.C. "A structure for deoxyribose nucleic acid." Nature 171 (1953): 737–738. Dembski, W.A. The Design Inference. Cambridge University Press, 1998.

Chapter 11 — The Factory

The ribosome is a molecular machine that reads the information in messenger RNA and assembles proteins one amino acid at a time. Every living cell contains ribosomes. Bacterial cells contain approximately 10,000 to 100,000; human cells on the order of ten million. Without ribosomes, no proteins are made. Without proteins, no cellular machinery functions. The ribosome is the foundational manufacturing platform of all life.

The bacterial ribosome consists of two subunits: the 30S small subunit (one RNA molecule and 21 proteins) and the 50S large subunit (two RNA molecules and 33 proteins). Together: 54 proteins and 3 RNA molecules working in precise coordination. The ribosome reads the messenger RNA codon by codon, recruits transfer RNA molecules carrying the corresponding amino acids, and catalyzes the peptide bond that links each new amino acid to the growing chain. The catalytic activity is performed by the RNA component—the peptidyl transferase center—not by a protein.

Ada Yonath, Thomas Steitz, and Venkatraman Ramakrishnan received the 2009 Nobel Prize in Chemistry for determining the atomic structure of the ribosome by X-ray crystallography. The structure confirmed that the ribosome is a precisely engineered machine with no tolerance for variation in its core catalytic components. Mutations in the peptidyl transferase center are lethal. The machine that builds all other machines must be present and complete before any other cellular machinery can be built.

Nobel Prize in Chemistry 2009: Ramakrishnan, Steitz, Yonath. nobelprize.org. Ramakrishnan, V. "Ribosome structure and the mechanism of translation." Cell 108 (2002): 557–572.