Information Layering

Steve M. Potter
9-19-97
steve.potter@bme.gatech.edu
http://www.neuro.gatech.edu/groups/potter/potter.html

I hear too often the phrase that DNA is the body's blueprint. It's not.

DNA doesnt say "Here's how to build a person." It is not a blueprint for an organism in the normal sense that we think of blueprints. In them, every detail is specified up front. Not so with DNA. It's as if DNA were more like a blueprint for a machine that seemed to have no purpose. From the looks of it, it certainly isn't for a building, not an architectual drawing at all, but a plan for a complex gadget. But parts of the plan don't make any sense unless you wear various different-colored glasses to read it. And you must lay the plans on a table and look at their reflection in a special, curved, lumpy mirror while standing on marks 1, 2, or 3 that are painted on the floor. Only from those postions do the wiggly lines on the paper appear straight in the reflections. And different sets of lines get straight depending which mark you are standing on. And different straight lines show up, depending on which glasses you are wearing.

So you do all this, and build the mysterious gadget. All it does is spew lots of numbers at you from its LEDs. What are they??? Why, they are Dewey-Decimal Numbers, of course! Call numbers for books! Followed by page numbers and word indexes and word counts. So you go look them all up, and, sure 'nuf, all the disjoint words and phrases and sometimes whole sentences, when appended to each other in order, make a story. What kind of story? It is another plan! It's instructions for how to build another gadget. It is a big drum filled with many little cards with small tasks for construction workers on them. One small task per card, like "Now cut 37 planks 8 feet long, from 1x12 stock," but some common tasks on many cards. The gadget has a voice and a hand for reaching in and pulling out cards. So you plug in the gadget, and turn it on, and the drum turns while it asks you a question, through its voice synthesizer, the cards tumbling over each other.

It asks, "When was the last time you had a banana split?" and gives you 5 choices, since there are 5 buttons to push. "(A) Yesterday, (B) Within the last week, (C) Within the last month, (D) Within the last year, (E) Never." So you are upset that you must choose (E), since you had one 5 years ago, but figure that is the best of the 5 answers. When you push (E), the drum stops, and the mechanical arm moves to the "E" door, opens it, and grabs a card. So you keep repeating the process. It keeps asking you personal questions. You answer them and get a card. The cards, when read in order, are a complete step-by-step instructions for constructing a building. A building that was never drawn on paper. But one that is nevertheless beautiful and aesthetic and functional when completed. It is the perfect house for you!

That is what DNA is like.

The most important misconception about DNA is that all the info is in the double-helix. It is not. Very little of it is. Very little. Just enough to make the first gadget--but not even that, because you have to have lots of info already to even make sense of the plans. You need to have the marks, the mirror, and the glasses.

The DNA is part of a process that includes many interations. Lots of specfic interactions. First, between the fertilized egg's proteins and the DNA. And all the other chemicals in this zygote. After a few cell divisions, the cells start to interact with each other because of their position, stress and strain, the genes that are active in them, etc. The cell-cell interactions allow more changes in subsequent generations of cells.

At all levels, molecules to cell groups, the laws of physics are imposing on the systems, making more specific interactions possible. Like the long-range tug of charged groups on two proteins brings them close enough for Vanderwaals forces to take over and hold them together in a functional pair.

And the developing organism takes in information from its environment. Germs tell the immune system how to develop. Sensory input tells the nervous system how to develop. Sunlight tells the pigmentation how to distribute itself.

No organsim grows from just a strand of DNA. DNA is always situated in an environment--a cell full of info-rich molecules, in a universe with info-rich laws of physical properties of matter and energy.


[From 7-19-94 entry in my Precious Stone journal]
[See also Douglas Hofstadter's excellent chapter on protein translation (Ch.27) in his other masterpiece, Metamagical Themas]