Rethinking the gene

An Austrian monk sits alone with his garden pea plants, recording if they’re yellow, green, round or wrinkly. He starts noticing simple patterns in how various traits appear in each generation: a yellow parent often produces yellow offspring, but two yellow parents can produce green offspring, and yellowish-green offspring simply don’t exist. From his observations he concludes that heritable properties are distinct units independently passed from parent to offspring—units that, many years after his death, will be called “genes.”

The seminal ideas of the monk Gregor Mendel fundamentally changed how scientists thought about inheritance. These concepts still provide the foundation for genetics taught in school textbooks, presented in newspaper articles and understood by the general public. But it may be time to move beyond Mendel’s valuable, but rather simplistic ideas. Research in genetics and developmental biology is complicating the typical notion of genes.

Currently, the public views genes primarily as self-contained packets of information that come from parents and are distinct from the environment. “The popular notion of the gene is an attractive idea—it’s so magical,” said Mark Blumberg, a developmental biologist at the University of Iowa in Iowa City. But it ignores the growing scientific understanding of how genes and local environments interplay, he said.

With the rise of molecular biology in the 1930s and genomics (the study of entire genomes) in the 1970s, scientists have developed a much more dynamic and complex picture of this interplay. The simplistic notion of the gene has been replaced with gene-environment interactions and developmental influences—nature and nurture as completely intertwined.

But the public hasn’t quite kept up. There remains a “huge chasm” between the way scientists understand genetics and the way the public understands it, said David Shenk, an author who has written extensively on genetics and intelligence. In his recent book The Genius in All of Us, Shenk explains that the public still thinks of genes as blueprints, providing precise instructions for each individual. Newspaper headlines touting “the gene for X” only perpetuate the blueprint metaphor.

“The elegant simplicity of the idea is so powerful,” said Shenk. Unfortunately, it is also false. The blueprint metaphor is fundamentally deceptive, he said, and “leads people to believe that any difference they see can be tied back to specific genes.”

Instead, Shenk advocates the metaphor of a giant mixing board, in which genes are a multitude of knobs and switches that get turned on and off depending on various factors in their environment. Interaction is key, though it goes against how most people see genetics: the classic, but inaccurate, dichotomies of nature versus nurture, innate versus acquired and genes versus environment.

Belief in those dichotomies is hard to eliminate because people tend to understand genetics through the two separate “tracks” of genes and the environment, according to speech communication expert Celeste Condit from the University of Georgia in Athens. Condit suggests that, whenever possible, explanations of genetics—by scientists, authors, journalists, or doctors—should draw connections between the two tracks, effectively merging them into one. “We need to link up the gene and environment tracks,” she said, “so that [people] can’t think of one without thinking of the other.”

Part of what makes these concepts so difficult lies in the language of genetics itself. A recent study by Condit in the September issue of Clinical Genetics found that when people hear the word genetics, they primarily think of heredity, or the quality of being heritable (passed from one generation to the next). Unfortunately, the terms heredity and heritable are often confused with heritability, which has a very different meaning.

Almost as bedeviling as the word gene, heritability has single-handedly muddled the discourse of genetics to such a degree that even experts can’t keep it straight, argues historian of science Evelyn Fox Keller at the Massachusetts Institute of Technology in her recent book, The Mirage of a Space Between Nature and Nurture. Keller describes how heritability (in the technical literature) refers to how much of the variation in a trait is due to genetic explanation. But the term has seeped out into the general public and is, understandably, taken to mean heritable, or ability to be inherited. These concepts are fundamentally different, but often hard to grasp.

For example, let’s say that in a population with people of different heights, 60 percent of the variation in height is attributable to genes (as opposed to nutrition). The heritability of height is 60 percent. This does not mean, however, that 60 percent of an individual’s height comes from her genes, and 40 percent from what she ate growing up. Heritability refers to causes of variations (between people), not to causes of traits themselves (in each particular individual). The conflation of crucially different terms like traits and variations has wreaked havoc on the public understanding of genetics.

The stakes are high. Condit emphasizes how important a solid understanding of genetics is for making health decisions. Whether people see diabetes or lung cancer as determined by family history or responsive to changes in behavior depends greatly on how they understand genetics. Policy decisions about education, childcare, or the workplace are all informed by a proper understanding of the dynamic interplay of genes and the environment, and this means looking beyond the Mendelian lens of heredity. According to Shenk, everyone in the business of communicating these issues “needs to bend over backwards to help people understand.”