What Do Organisms Mean? > Getting Over the Code Delusion > Summary
A project by Stephen L. Talbott

Next >

Getting Over the Code Delusion


IT IS NOW WIDELY RECOGNIZED that the Human Genome Project (HGP) failed to yield anything like a DNA “Book of Life”. As molecular biologist Tom Misteli wrote in the journal Cell, the project “shed little light onto the Holy Grail of genome biology, namely the question of how genomes actually work”. It did not reveal the immaculate, computer-like logic that was supposed to give organisms their marching orders. Instead, it has shown DNA inextricably woven into, and regulated by, virtually all the processes — all the life — of the cell.

The HGP brought vivid attention to paradoxes both old and new. First, it turned out that we share between 98 and 99 percent of our protein-coding genes with chimpanzees, leaving many to wonder how to explain our differences — or even whether there were any very significant differences. Second, it now became indisputable that humans have no more genes than some much simpler organisms. (The water flea has more than one and a half times the number of our genes.) Third, some 95 - 98 percent of the human genome does not bear the protein-specifying genetic “code” at all, but was dismissed at first as “junk DNA”.

And all this brought renewed confrontation with a fourth, long-perplexing truth: cells originally possessing the same genome in our developing, embryonic bodies eventually differentiate into hundreds of distinct cell types, suitable for lungs, livers, bones, blood, retinas, and so on. If DNA makes us what we are, how can the same DNA produce such radically different cellular features?

Part of the answer is now often said to be that the so-called junk DNA actually performs vital regulatory functions to help make the differentiation of cells possible. But, of course, the junk DNA is also the same in the different cell types, so that doesn’t get us very far. The more profound answer is that gene regulation in general is distributed throughout the cell and organism. Cells with the same DNA can become very different because the organism directs the functioning of its DNA at least as much as the DNA directs the functioning of the organism. The power of being what it is lies with the organism as a who