Recently, Greg Laden put up a list of falsehoods to which I added a few others which needed explaining, among them is my assertion that DNA is not information (or code, or instructions, etc). I intend, hopefully, to support this claim with more fluent logic than done via email.
1: DNA is the double stranded template molecule of material heredity
The “information metaphor falshood” (IMF) is a useful falsehood when used properly, but is overly simplistic. DNA is like instructions in that cells follow predictable patterns due to the pivotal role this molecule plays in the assembly and production of RNAs and proteins. Beyond this, however, IMF breaks down. The sequence of the DNA molecule does not contain instructions, but rather is a physical structure which responds to interactions with other molecules because of this structure, not because of the sequence. While the sequence partially provides this structure in DNA, this structure is influenced by many factors. For example, histones around which the DNA is coiled play an integral part in what segments are expressed. Sequences of DNA are only partially responsible for the structure of these histones and they are regulated by other external and internal factors aside from other segments of DNA. The IMF is a simplified version of what is actually occurring within the cell and this simplification ignores the three-dimensional and interactive aspects of the molecules within the nucleus. Additionally, IMF assumes that the sequence is the important aspect of DNA ignoring that many sequence changes in DNA do very little to the organism. DNA can be better described for what it is, a molecule which provides the templates for the synthesis of various RNAs under specific conditions. It is not a causative agent or “set of directions” but an interacting part of the cell (albeit an important one) subject to external and internal factors.
2: Information (instructions, code) exist upon the conscious perception of them.
For example, a cookbook written only in English would not be directional or instructional to a person unfamiliar with the language. Just because we are capable of explaining many aspects of DNA as being “instructional” or “coded” does not mean it is actually a code or an IKEA booklet to assemble a chair. Codes and instructions describe, to a conscious and understanding observer, they are not the mold to make the parts and all necessary tools. I’ve often heard that “DNA is analogous to machine code” because both contain sequences which explain precisely how to do a certain task. As I have previously stated, however, DNA does not describe or instruct the cell on what to do, it is the reactive template which responds under certain conditions. Also, while instructions convey meaning and intentionality, DNA provides neither.
3: IMF relies upon known and blatantly false simplification to reach the conclusion
The information metaphor implies that the important aspect of DNA is only the sequence or “content” while ignoring three-dimensional conformations and external influences. Parts of the DNA molecule which have useless sequences, but the lengths are important (separating promoters) as well as regions providing specific binding to histones which allows interaction at other specific points along the molecule are also important.
Finally, “information” implies directionality or intentionality while DNA is not a causative agent nor was it placed, put, or designed by any agent. Instead, it is hereditary material which has been shaped by countless generations with mutation and evolution influencing it. DNA is not a pattern which “represents” or “conveys” anything. It is a template which functions as hereditary material enabling and regulating RNA synthesis.
IMF…the international monetary fund?
No, that IMF is even more useless than this one…
Wow, that totally makes sense to my brain. The “information” metaphor never seemed quite right to me. Thanks for the explaination for non-scientist dummies like me.
Well, without an intentionality or directionality, nothing is really “information.” Similarly, you can argue for the same reason, it is not a “code.” It is useful to describe this way for simplicity, but it is does not fit with reality. We use the “genetic code” to predict what proteins will result from a given sequence, it’s more of a theory of genetics than an actual code. It is also FAR more complex than many can even begin to contemplate. Examples: selenocysteine, β-alanine, and pyrrolysine. Also, another fun fact: cytosine spontaneously deaminates resulting in uracil, so all these cool little repair mechanisms exist to enforce the fourth commandment of the nucleus [Thou shalt not have uracil in your DNA]. Ironically, just like those commandments of old, all genetic commandments are broken, so they’re more like guidelines, really…
UGA means stop? Not if there is a special stem-loop structure (called SECIS). UAG means stop, too? Well, there’s another stem-loop override for that one to insert pyrrolysine. AUA means isoleucine, not in mitochondria. Again, you see an example of the STRUCTURE overriding the sequence. Stem-loop forms=keep on synthesizing protein; no stem-loop, then it’s a stop.
You are right about complexity but way off base with information content. To say the genomes of life do not convey information – in the way of structural codes that integrate chromatin- bound DNA to the nucleoskeleton, regulatory codes that define transcription factor binding sites, protein coding sequence that specify the proteome, and miR codes that are transcribed into small fine tuners of the proteome – is tantamount to saying there is little meaning in what you and I are writing.
BZZZZZZZZZZZZZZZZZZZZZZTTTTTTTTTTTTTTTTTT!
Wrong.
That’s still not “information.” Those are physical conformations in response to biochemical conditions, enzymatic activity, and mechanical action of proteins. It STILL isn’t “information.” It’s still not coding for anything. It is a useful metaphor for explaining this, but it does not represent the reality of the situation.
Also, you came here via a search for “DNA is quaternary code,” it seems your pre-existing notions that DNA was code interfered with your ability to read my statements and present well structured arguments against it. Congratulations on learning to argue by metaphor, let’s try arguing with reality next.