In my first post on Meyer’s Signature in the Cell I discussed information theory, and claimed that the cell exhibits functional information—information that cannot be explained in terms of the physical machinery of the cell.  In this post I want to provide some background on the machinery and inner workings of the cell to provide evidence for the claim that the cell contains complex specified information (functional information), and explain why biologists have come to recognize that DNA stores and transmits “genetic information,” contains a “genetic blueprint” with “assembly instructions,” and expresses a “digital code.” 

The two most basic components of the cell are DNA and proteins.  DNA is made up of a 4 character chemical alphabet: adenine, thymine, guanine, cytosine (these are called nucleotides).  These nucleotides always appear in complimentary pairs: adenine is paired with thymine, and guanine is paired with cytosine. 

Proteins—the workhorses of the cell—are composed of amino acids.  The cell contains 20 different kinds of amino acids.  To create functional proteins, these amino acids must be sequenced together in a specific order, forming a “chain” of amino acids (proteins come in varying lengths, with shorter proteins consisting of ~100 amino acids, most proteins consisting of several hundred, and some as large as 34,350 [titin]).  While there are a number of ways in which amino acids can be sequenced, the vast majority of combinations are functionless.  They sequence must be specified if the protein is to have function (functionality also requires the protein to be folded into a particular shape).

(more…)