“Code” may be defined as any of the following:
1) a set of rules for converting information into another form or representation (encoding) for later retrieval
2) a set of rules or principles or laws (not applicable in this case)
3) a system of transmitting messages for brevity and/or security (also not applicable)
4) the symbolic arrangement of data or instructions in a computer program or the set of such instructions
Is DNA a code?
A DNA molecule is, itself, neither a set of rules, nor is it symbolic of data or instructions. DNA molecules are sequences of nucleotides which can be broken down into reading frames, promoters, enhancers, structural and spacial segments, and so forth. Since the DNA molecule has such variability and physical functionality inherent within it, the metaphor of DNA being information or a “code” is both overly simplistic and inaccurate.
What about RNA?
Additionally, functional segments of the “code” exist without ever being “decoded.” Some segments of RNA, for example, spliceosomes, ribozymes, and ribozomes are in the same sequences as the DNA template. Even ignoring the function inherent in many RNA transcripts (spliceosomes, ribozymes, ribozomes, etc.) which are still “the raw code,” we can continue on both ends. The DNA sequence itself, as well as the transcripts which are translated into proteins, are similarly not information. While codes rely upon symbolic arrangements to transmit data or instructions, the arrangement of DNA merely serves as a template by which RNA transcripts are made; this is more like a mold than a code as the resulting copy of a DNA template is the reverse and opposite of the template itself: the DNA sequence 5’AAGCTTGGCAT3′ is transcribed into the RNA sequence 5’AUGCCAAGCUU3′. What, also, is the magical “information” this DNA sequence is supposed to carry? Thus far, it appears the RNA is not information, nor is the DNA itself information.
Could it be the proteins which result from some RNA transcripts which are the “information” in DNA? No. Proteins also do not transmit information; while the protein is useful, it is as much “information” as a car is a manual to assemble a new one. Proteins were never “encoded” from protein to RNA to DNA in order to be properly “decoded,” the function of a protein is based upon its physical structure, as is the function of RNA and DNA.
Well, what is the “genetic code?”
We hear this phrase all the time, mostly by individuals who have no understandings of even the basics of genetics. The genetic code is the means by which we (humans) organize DNA into bits which we can understand. We remove the three-dimensional context and focus exclusively on the sequence. From this, the simplistic explanation (DNA->RNA->”magical protein”) that DNA is arranged in codons. These codons hold the “magical information” which becomes “magical protein,” which as we all know, is what DNA is all about. This is where the confusion lies. DNA does not just contain sequences for protein; functional units exist outside of any reading frames including promoters, enhancers, suppressors, etc. Other functional segments exist as well (centromeres, telomeres, and origins of replication) which contradicts the idea that DNA is like a software program. The genetic code is, in this respect, a human construct to understand specific regions of DNA which do contain sequences used for protein production. This is the only use this phrase has.