At the same time, it’s also not surprising that many people get nervous at the prospects of that scientific milestone. It will no doubt be a revolution, but there are some scary “Brave New World” overtones that raise fundamental questions about how we will think about ourselves. Will it mean that our behaviors, thoughts and emotions are merely the sum of our genes, and scientists can use a genetic roadmap to calculate just what that sum is? Who are we then, and what will happen to our cherished senses of individuality and free will? Will knowing our genetic code mean we will know our irrevocable fates?
I don’t share that fear, and let me explain why. At the crux of the anxiety is the notion of the Primacy of Genes. This is the idea that if you want to explain some big, complex problem in biology (like why some particular bird migrates south for the winter, or why a particular person becomes schizophrenic), the answer lies in understanding the building blocks that make up those phenomena–and that those building blocks are ultimately genes. In this deterministic view, the proteins unleashed by genes “cause” or “control” behavior. Have the wrong version of a gene and, bam, you’re guaranteed something awful, like being pathologically aggressive, or having schizophrenia. Everything is preordained from conception.
Yet hardly any genes actually work this way. Instead, genes and environment interact; nurture reinforces or retards nature. For example, research indicates that “having the gene for schizophrenia” means there is a 50 percent risk you’ll develop the disease, rather than absolute certainty. The disease occurs only when you have a combination of schizophrenia-prone genes and schizophrenia- inducing experiences. A particular gene can have a different effect, depending on the environment. There is genetic vulnerability, but not inevitability.
The Primacy of Genes also assumes that genes act on their own. How do they know when to turn on and off the synthesis of particular proteins? If you view genes as autonomous, the answer is that they just know. No one tells a gene what to do; instead, the buck starts and stops there.
However, that view is far from accurate too. Within the staggeringly long sequences of DNA, it turns out that only a tiny percentage of letters actually form the words that constitute genes and serve as code for proteins. More than 95 percent of DNA, instead, is “non-coding.” Much of DNA simply constitutes on and off switches for regulating the activity of genes. It’s like you have a 100-page book, and 95 of the pages are instructions and advice for reading the other five pages. Thus, genes don’t independently determine when proteins are synthesized. They follow instructions originating somewhere else.
What regulates those switches? In some instances, chemical messengers from other parts of the cell. In other cases, messengers from other cells in the body (this is the way many hormones work). And, critically, in still other cases, genes are turned on or off by environmental factors. As a crude example, some carcinogens work by getting into cells, binding to one of those DNA switches and turning on genes that cause the uncontrolled growth that constitutes cancer. Or a mother rat licking and grooming her infant will initiate a cascade of events that eventually turns on genes related to growth in that child. Or the smell of a female in heat will activate genes in certain male primates related to reproduction. Or a miserably stressful day of final exams will activate genes in a typical college student that will suppress the immune system, often leading to a cold or worse.
You can’t dissociate genes from the environment that turns genes on and off. And you can’t dissociate the effects of genes from the environment in which proteins exert their effects. The study of genetics will never be so all encompassing as to gobble up every subject from medicine to sociology. Instead, the more science learns about genes, the more we will learn about the importance of the environment. That goes for real life, too: genes are essential but not the whole story.
