Things I Never Knew About Genetics

Years ago in high school biology, I learned about Gregor Mendel, the Augustinian monk who discovered genetics through his work with pea plants. Dr. Mendel bred pea plants and took careful note of shared characteristics between “parents” and “offspring.” After a great deal of experimentation, he determined that there were two genes for every trait. Dominant genes found expression whenever one gene was present in the pair; recessive genes needed to be a matched pair to manifest. Armed with this understanding, he was able to breed selectively for certain traits.

Dr. Mendel’s work set the foundation for the modern science of genetics. It teaches us that our human characteristics are the product of genetic contributions from our fathers and mothers. It explains why certain traits are more common than others – e.g., brown versus blond hair. It also informs the practice of modern medicine given the weight accorded family history when assessing potential health threats.

In their book Ultra-Prevention: The 6-Week Plan That Will Make You Healthy for Life, Dr. Mark Hyman, MD and Dr. Mark Liponis, MD argue that genetic inheritance is far less important than lifestyle choices in determining our well-being and risk of life-threatening disease. They note that while some traits (e.g., gender, race, eye color) are controlled by a fixed pair of genes, most are determined by interactions among many genes within a context that is vastly more complex than a pea plant. As such, genetic code does not always translate into genetic expression. As a proof source, Drs. Hyman and Liponis cited a Scandinavian study that assessed 44,000 pairs of identical twins to determine the genetic underpinnings of cancer. Researchers concluded that only 10% of cases could be linked to genetic inheritance. The rest were associated with lifestyle choices.

DNAI was intrigued, so I picked up a booked entitled Epigenetics: The Ultimate Mystery of Inheritance, by Richard C. Francis. Epigenetics is the study of changes in organisms caused by variations in gene expression rather than alterations of the genetic code. By combining the two readings, I have a new (rudimentary) understanding of human genetics. Here goes…

Virtually every cell in our bodies contains an identical set of the 30,000+ genes from which the body can make over 300,000 proteins. These proteins include enzymes, antibodies, structural proteins, messenger molecules, receptors, hormones, cytokines, and others. They provide structure to maintain our bodies. They control the process of energy production, and they support cellular and organ function. While this vast information warehouse remains unchanged throughout our lifetimes, cells make the determination regarding which genes to engage (and not engage) when making proteins. These decisions are influenced by:

  • The functions that cell typically performs
  • The needs of the body at that moment in time
  • The cellular processes in effect at that time – e.g., growth, repair, regeneration, reproduction
  • The cellular environment

In simple terms, each gene has two core components: a protein-coding sequence (“manufacturing blueprints”) and a control panel. Genes activate when certain chemicals bind to their control panels. The cellular environment establishes conditions through which this engagement is more or less likely. For example, the presence of another organic molecule may inhibit access to a gene’s control panel, thereby rending its template inactive. The cellular environment is also affected by the surrounding cells with which it interacts and distant cells with which it communicates via the bloodstream. It’s also affected by the external environment. For example, if a pregnant woman experiences chronic stress, she’ll produce excess cortisol that will pass to the fetus via the placenta. Excess cortisol insinuates itself into the fetus’ cellular environment and will make the baby more sensitive to stress.

This discussion gives rise to a couple of new additions to my vocabulary, courtesy of Webster’s New World Dictionary. A genotype is “the fundamental constitution of an organism in terms of its hereditary factors” – i.e., its genetic material. A phenotype is “the manifest characteristics of an organism that result from both its heredity and its environment.” The phenotype reflects the expression of the genotype and includes such factors as skin thickness, speed of reflexes, metabolic rate, blood pressure, good/bad cholesterol, and other health indicators. While we can’t change our genotype, we can exercise a great deal of control over our phenotype!

Take, for example, a gentleman who has a genetic predisposition for heart disease. If he consistently makes healthy lifestyle choices, he may never develop a coronary condition. In fact, Dr. Dean Ornish, MD and Dr. Caldwell Esselstyn, MD demonstrated that severe heart disease can be arrested or reversed through lifestyle changes! Drs. Hyman and Liponis also note that persons who eat healthy food and avoid antibiotics tend to maintain good gut bacteria. These bacteria promote activation of a cancer suppressor gene that reduces the risk of colon cancer.

Bottom Line: We can affect our gene expression by improving our physical and cellular environments through diet, exercise, and other lifestyle choices. We don’t have to become what we inherited!