Saturday, September 03, 2011

Richard Francis - Epigenetics: The Ultimate Mystery of Inheritance


I've been meaning to post these reviews for a while now - epigenetics is changing a lot of what we have previously assumed about evolution and how genes are impacted by the environment. Turns out that genes can be altered in a single lifetime. For example, how a mother eats before and during her pregnancy - and how the father eats prior to conception - can change the genetics of their child in significant ways.

This book by Richard Francis, Epigenetics: The Ultimate Mystery of Inheritance, has received some good reviews - I'm looking forward to reading it. Here are three reviews.

Mixing Nature and Nurture

by Julia M. Klein
JUNE 21, 2011  

In the waning months of World War II, the Nazis, angered by Dutch resistance, retaliated with a food embargo. As a result, 22,000 people in western Holland starved to death. And the effects of the famine were not limited to a single generation. The children of malnourished mothers were born undersized. More surprising, studies found that, as adults, these men and women were more susceptible to a wide range of ailments, from diabetes and depression to breast cancer and obesity.

Neither classical genetics nor an environmental explanation suffices to unravel this phenomenon. But the new science of epigenetics – which deals with long-term alterations in gene behavior – supplies a key causal link. Epigenetics involves chemical changes in cells, sometimes random and sometimes environmentally caused. What is even more startling is that these epigenetic “marks,” as they are called, can be inherited – either directly (much like genetic mutations) or in various indirect ways.  

Richard C. Francis, a neurobiologist turned science writer, has written what he says is the first popular book on this booming, cutting-edge field. Even so, reading Epigenetics: The Ultimate Mystery of Inheritance (Norton) requires an almost scholarly level of concentration. It helps to have, at the very least, a working knowledge of genetics. If the mere mention of messenger RNA, alleles and methylation (this last was new to me, too) induces panic, then this slim, intriguing volume will provoke anxiety for sure. 

To his credit, Francis, relying heavily on analogy and example, does a mostly masterful job of illuminating some very thorny concepts. He introduces epigenetics with a reference to “identical,” or monozygotic, twins. We expect such twins, who are genetic clones, to be biologically similar. But there are powerful exceptions. In the instance that Francis cites, one twin was born with a disorder of sexual development known as Kallmann syndrome, while the other appeared normal.

Read the whole review at Obit.

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Lamarck's Revenge

by Judith Shulevitz
August 18, 2011
Epigenetics: The Ultimate Mystery of Inheritance
by Richard Francis
W. W. Norton & Company, 234 pp., $25.95

THERE HAS BEEN a revolution in the world of genetics. It is called epigenetics. The Greek prefix “epi” implies something that comes in addition to something else; epigenetics adds to the study of genes the study of how they get turned on or off. Although a Martian eavesdropping on conversations about genetics in the popular media would surely conclude that genes and traits correspond in a one-to-one ratio, in reality the twenty thousand to twenty-five thousand genes in the human genome do not automatically spawn traits. Genes have to be turned on, or “expressed,” through a complex process that takes place in the cell, before they can encode instructions that will (in combination with other genes) affect the shapes of bodies, or their metabolic rates, or what have you. Genes can also be turned off, or “silenced.” Gene expression and gene silencing take place all the time, as a matter of course. The science writer David Shenk recently came up with this delightfully mad-scientist metaphor for the process: “Think of a giant control board inside every cell in your body. Many of those knobs and switches can be turned up/down/on/off at any time.”

Now that geneticists—along with neuroscientists, cognitive psychologists, and others who study development—have broadened their focus from the naked double helix (that is, the DNA) to the chemical attachments that make up all those knobs and switches, they must grapple with a force long thought to have little direct impact on genetic inheritance: the environment. Epigenetic processes react with great sensitivity to genes’ immediate biochemical surroundings—and even more surprisingly, they pass those reactions on to the next generation. This biochemical stew in turn reflects what organisms ate, drank, breathed, swam in, or felt. In other words, your genome is being affected by your social reality—by whether you live in a clean suburb or dirty city, eat fresh food or junk, and feel empowered or embittered by your station in life—and is likely to pass some sort of epigenetic memory of that experience to your offspring.

As paradigm shifts go, this is huge.

Read the whole article at The New Republic.

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Goodbye, Genetic Blueprint - What the new field of epigenetics reveals about how DNA really works.

Richard C. Francis. Click image to expand.

There are almost as many metaphors for genes as there are genes. One of the most familiar, and the hardest to let go of, is the tidy blueprint, at once reassuringly clear and oppressively deterministic: Our genome is the architectural plan for who we are. It tells our body how to build itself, setting our height, our health, and even our moods since before we are born. Small wonder that we imagine if we can read our genome, we will discover not just the truth of ourselves but perhaps our future, too. Remember the high hopes that spurred on the Human Genome Project in the 1990s? Though the genetic catalog is now largely complete, we still await many of the anticipated insights, and in Epigenetics: The Ultimate Mystery of Inheritance, Richard Francis, a writer with a biology Ph.D., traces the emergence of a different genetic paradigm. Our DNA shapes who we are, Francis reports from the research forefront, but it is far from a static plan or an inflexible oracle; DNA gets shaped, too. For good or ill, the forces that determine our fate can't be captured by anything so neat as a blueprint.

Francis's primer introduces a new field, whose roots predate the rise of pure genetic determinism. How is DNA itself shaped? The search for answers begins in the late-19th-century work of scientists such as Hans Driesch, whose study of sea urchin embryos revealed that the cell plays a key administrative role in an organism's development. He discovered that if you take cells from one location in the embryo—the area that will become, say, the spines--and plant them in another—the mouth area--their function changes: You don't get spines growing out of the mouth, you get a normal mouth. A cell's identity doesn't arise from a preordained genetic recipe inside it. Crucially, it is the cues that a cell gets from neighboring cells that affect how the genes inside it behave.

Read the whole article at Slate.

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