The Secret Recipe

Posted: February 26, 2011 in biochemistry, evolution, genetics

I am guilty, along with countless texts, websites, experts, and novices, of an academic travesty – using an inaccurate simile to explain scientific phenomena. Namely, the description of genomic information as a blueprint and the body as the resultant structure.

Thank goodness I recently failed to notice The Agile Gene was merely a renaming of Nature Via Nurture, and was therefore conned into reading it again. It reminded me of what I already knew, but lie buried beneath the weight of my formal education… Our DNA is not a blueprint but a recipe. We are not built, but baked.

The building designed from a blueprint is literally the sum of its parts. A cake, however, or a human, is a whole greater than its sum; it takes on properties not obvious from the list of ingredients. What, asks Blumberg in Body Heat, is the essence of a chocolate cake? Is it the eggs? Flour? Cocoa? No, these are merely ingredients. Nor is it the pan, oven, or whisk. A recipe is clearly not a cake, either. What is the essence of a human? How can it be captured?

The reality is that simply unraveling our DNA does not explain how it works, any more than knowing the alphabet helps you to read a book (with apologizes to Charles Arthur).

It seems we expect too much of our limited understanding of DNA, which derives from the metaphors we use about it. When we can only describe something indirectly, it may falsely acquire the expectations realistic of the associated analogy. We therefore look to genes to solve riddles, fix problems, and explain mysteries. However, we forget that it just isn’t so simple…

Consider what the greatly missed writer Douglas Adams pointed out – Imagine that you were trying to describe how to make a fruit cake by writing the blueprint: currant here, surrounded by certain amount of air-filled cake mixture, and then more currants. It would be hellish. So how do we make fruit cakes? Not by blueprint. We use recipes – mix these things together, bake at a particular temperature for so long, and voila: if you’ve got the components right, you’ll have currants distributed satisfactorily around your finished product.

Think about it: Bakers use, by and large, the same ingredients in many recipes to produce a wide variety of unique confections. The art of baking lies in the ratio of flour to sugar to eggs to salt, and such; not in using different ingredients for each different recipe. Can you predict the precise structure, placement of parts, consistency, etc. of the product just by looking at a recipe? Nope.

Likewise, many organisms share many genes, probably from a common ancestor. We change around the timing, intensity, and location of gene expression, throw in a few special touches, and viola! become unique individuals. But it isn’t just genes that make us who we are – environment clearly affects the expression of genes.

Okay, so you’ve made the cake batter or bread dough or what have you – now what? The oven condition and quality, local elevation, humidity, etc. all have significant impacts on the final product. Some cooks create masterpieces at low temperatures for a long time; others dazzle with short durations of high heat.

The secret ingredient we’re often missing when we describe our genes as a blueprint is quite possibly that elusive fourth dimension, forgotten usually by its continuous presence – time. You can break a structure back down into its constituent components; you cannot unbake a cake. Or a person.

One of my favorite analogies used by Ridley is: You and I and other animals share the genes necessary to make vertebrae. This neck sauce, as he calls it, is used to marinate giraffes for a much longer time during their development than us people; yet we too were briefly soaked in that sauce. Snakes are basted in the marinade during their entire development and thus end up with a neck the length of their body! But each of us express the same neck genes in our neck region; the difference is how long, and how much marinade we soaked in as we developed. You see, we were not assembled, we were concocted.

If something disrupts our proper development, or throws off the timing of gene expression, then that something has the potential to cause disorders and disabilities. We are the products of the conditions in which our genes are expressed; not only that, but the conditions we find ourselves in further influence future directions of gene expression.

As the psychologist Gary Marcus has pointed out in yet another attempt at an applicable analogy by which to understand something not quite understandable, genes function like IF-THEN lines of code in a computer program. The IF refers to the regulatory portion of the gene and THEN refers to the protein template region.

Comments
  1. Claire says:

    Do tell…

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