The following post is the first in our series of entries submitted for the 1st Annual Lions Talk Science Blog Award. This piece is by Lina Jamis, a student in the Anatomy Graduate Program.
Researchers who study genetic interactions—of which there are thousands currently under study and billions more to be studied—often find themselves trying to explain their field to non-technical audiences.
And if there’s anything I’ve learned as a student who has taken various levels of human genetics as an undergraduate and now at the graduate level, it’s that the average person has many preconceived notions about genetics that are mostly inaccurate, if not altogether wrong. These misconceptions are often perpetrated and perpetuated by our educational systems and media that aim to simplify a field that is intrinsically un-simple.
There are few absolute truths when it comes to human genetics. Absolutely, there are disease genes, but there are also modifiers of disease genes, and modifiers of modifiers of disease genes. It goes on. Incomplete penetrance, genetic heterogeneity, pleiotropy, and gene-environment interactions—these are just some of the factors that make studies of relatively simple-seeming genetic diseases extremely challenging.
Take eye color, for example. Students learning introductory biology are taught that eye color is a simple trait and that blue eyes are recessive, while brown eyes are dominant. This leads people to believe that blue-eyed couples can only have blue-eyed children and that a brown-eyed parent’s brown eyes will always be more penetrant (or more expressive in his or her children) than his or her lighter-eyed partner. This idea is not totally false, but again, it’s not totally true either. The idea that blue eyes are recessive is an idea that is based on patterns of inheritance from hundreds of studies, but if there’s anything we know about inheritance, it’s that it’s not always simple. Most if not all traits are influenced by interactions of many genes. This is further complicated by the idea that gene-environment interactions are also thrown into the mix, an idea called epigenetics, that is gaining more and more traction with increasing evidence of its powerful effects on gene expression.
It is therefore of absolute vitality that we understand genetic concepts and clear misconceptions that run rampant in education, media, and even scientific literature. Simply put, our futures depend on it. Consider the genetic engineering industry. It’s a field that’s built on the pretense that scientists not only understand, but can also anticipate the functions of the DNA sequences that they isolate or manufacture themselves and express in constructs or model organisms. If we can’t understand genetics in a basic way, then how can we expect to become masters of genetic manipulation? How are we to judge others when we pinpoint traits such as sociability, intelligence, and criminality as the result of our genetic codes? How do we treat individuals who are found to have predispositions to disease states? These lines of thinking belong to what can be called the gene myth, namely, a widespread cultural thought that says ‘it’s all in the genes,’ an idea that is ultimately deterministic wherein we assume that DNA acts like a puppeteer and we have no choice but to dance on strings like a puppet.
The gene, which is the central icon of our time, is simultaneously a material object and an ideology—one that is full of potential but possibly danger if we refuse to understand it correctly.
Below, I’ll outline some of my favorite gene myths and try to help debunk them:
1. Genes are the sole determinants of traits.
Few traits such as blood type are determined strictly, we think, by genetics, but most traits are in fact both influenced by genes and the environment in which we live. Furthermore, we don’t necessarily inherit a disease, per say, but instead inherit susceptibility factors that increase the risk for a disease. A person may be genetically predisposed to obesity due to family genetics. However, lifestyle choices can be made that minimize the actuality of becoming obese. The same situation works for many predispositions to diseases—alcoholism, Alzheimer’s disease, heart disease, etc. Saying that genes is the reason for particular disease states removes our accountability for taking control of choices in our lives that can actually lessen or reverse such states.
2. Single gene, single trait.
Multiple genes, not just a singular gene, determine most traits in humans. When a trait is controlled by more than one gene, it is called polygenic. Traits that are polygenic exhibit a range, which is why we see a continuum for physical traits such as height and skin color. Consider that we all contain genes that control the production of melanin, the pigment most commonly associated with skin color, but also consider that we all contain genes that modulate the genes that control the production of melanin, resulting in different amounts of melanin produced as well as the type. Mendelian genetics taught us that brown hair is dominant to blond hair. Often this lesson is accompanied by a Punnett square filled with lowercase and uppercase letters to explain this point, but we now understand that inheritance of pigmentation, like many other traits, is much more complex and cannot be explained in a simple, single-gene Punnett square. Instead, we must resign ourselves to the fact that every single trait is most likely coded by many genes, whose interactions remain in that deep part of the iceberg that we might never see from the surface.
3. Once a mutation is discovered, it can be fixed.
Oh, how many scientists, physicians, researchers, and patients wish this was true! Once a mutation has occurred in the genome, it cannot be “fixed”—rather it might show itself in the individual or it might not. Since a method to reverse the appearance of mutations does not currently exist, most therapies focus on discovering drugs or other interventions that counteract the malfunctioning gene. Huntington’s disease is a perfect example of this phenomenon. Although caused by the incorrect repetition of the sequence ‘CAG’ within the huntingtin gene, there is still no cure. Until then, there are experimental techniques underway that may allow gene insertion to treat disorders. At this point, most research on replacement gene therapies exist in model organisms with the hope of eventually targeting disorders in human individuals.
4. Only certain people have disease genes.
Genetic diseases are caused by mutations in genes that exist in all of us. For example, popular science journals discuss “the breast cancer gene,” BRCA1. But the fact is that all of us, men and women, alike, have the BRCA1 gene. The normal function of BRCA1 is to produce a protein that helps to repair DNA damage. Individuals that have a malfunctioning version of BRCA1 are more likely to allow the accumulation of DNA damage because of inefficient repair. Testing positive for cancer is testing positive for the mutant allele of a particular gene such as BRCA1; it does not imply the presence of an altogether new gene that is absent in those who do not have cancer.
Maintaining a greater grasp on the misrepresentations that frequently accompany genetics is vital to combatting a) scientific illiteracy in the field of genetics and b) exploding the popular image of the gene as the all-determining factor in the human condition. The idea is not to belittle the gene, but to point out the fact that it’s actually exponentially more complicated than we previously thought. By adopting this perspective of the gene, we respect its potential recognize not only what we know about genes, but ultimately, what we don’t.