Guest Columnist
John Richard Schrock
Epigenetics Expands Genetics
Major human blood types (there are many more) include Type A (AA or Ao), Type B (BB or Bo), Type AB (AB) and Type O (oo) and a second important Rhesus factor of Rh positive (++ or +-) or Rh negative (- -). If you had a good biology teacher, you learned that some genes could be dominant (as in A, B and Rh-positive blood, or recessive as in Type O and Rh negative. While Gregor Mendel (1822–1884) founded the science of genetics, describing dominant and recessive “factors” (now called “genes”) in pea plants, Mendel died without recognition. Scientists did not understand his concepts until 1900.
Genetics advanced from fruit fly experiments to the discovery of DNA by Watson and Crick in 1953. Some traits were recognized as “polygenic” where many genes in different locations contribute to a trait such as human height or skin color.
However, in the 1990s, deeper research into cellular differentiation, long term historical records from the aftermath of world war starvation, cancer, and other biological evidence revealed that there are traits that are not explained by changes in the sequence of DNA comprising genes. But this does not overthrow Mendel’s genetics, because the changes that are “on top of” genetics (thus the name “epigenetics”) still work through the standard biological dogma where DNA is copied across to an RNA molecule which forms the sequences for producing proteins. These epigenetic changes occur due to modification of histones around the DNA, a chemical process called DNA methylation, and some other factors that cause the genes to express themselves differently. And “epistasis” is when one gene or variant changes the effect of another. In 2008, a Cold Spring Harbor meeting defined epigenetics as a “stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence.”
These are not simple concepts. To understand epigenetics without a biochemistry degree, I recommend “Epigenetics: The Ultimate Mystery of Inheritance,” by Richard C. Francis published by W.W. Norton in 2011. A freelance writer with a Ph.D. in neurobiology and behavior, Francis lays out a series of epigenetic situations based on their history of discovery. The final terminology is complex but these stories provide clearer meaning for non-scientists.
During WWII, the Dutch experienced a severe famine. Their detailed medical records revealed the subsequent effects on babies born to starving mothers. Ballplayer Jose Canseco’s use of steroids led to an understanding that the same genes could have different effects. Pregnant mothers (but not fathers) who experienced the destruction of the World Trade towers produced children with PTSD. And identical twins whether raised together or apart often have diverging traits. Many studies revealed that gene expression varied with birth weights and that changes in the histones around DNA could result in higher gene expression, and that these changes could be passed from a cell to its descendants. Folic acid given during pregnancy to reduce spina bifida has epigenetic effects beyond normal development. A classic experiment by Harry Harlow showed that baby rhesus monkeys deprived of parental care later became terrible mothers. This led to mouse lick-deprivation experiments that demonstrated lower expression levels for a related gene.
A total mis-use of epigenetics is described in Loren Graham’s “Lysenko’s Ghost: Epigenetics and Russia” published by Harvard University Press in 2016. Graham is a retired research associate of Harvard University and fluent in Russian. In this book, Graham interviewed Lysenko himself in 1971, after his anti-Mendelian views were discarded, along with other scientists who survived the Lysenko “acquired inheritance” tyranny. Yet epigenetics provides no resurrection of Lysenkoism since epigenetic factors all rely on alteration of DNA expressions even if they persist across several generations.
Beyond these books, a more serious distortion of epigenetics may be occurring in the U.S. Some now discourage teaching modern genetics, push the elimination of any concepts of phylogenetic branching related to “race,” and use the mis-use of eugenics in the early 1900s (and Nazi Aryan racism) to dismiss any parental concern about passing on clearly inherited disorders. Real labwork with fruit flies or other organisms clearly supports genetics. But those experiences are disappearing in the American school curriculum, often replaced with media and computer games that give perfect 3-to-1 hybrid ratios. Science relies on replication in reality.
But if Lysenko was alive today, he would have plenty of online fake science to teach.
