This book is interesting and notably competent science writing. The proper audience for this book is someone with specific interests in genetics, and biology.
The word, “epigenetics” refers to all those ways in which influences are imposed on the genetic codes in DNA in our cells. Unfortunately, as Nessa Carey reminds us on page, 101, the word has been used in many different ways, and therefore a book on epigenetics ends up resembling a book called, “Many Topics About Genetics and Biology.” One of the strong points of this book is the author’s determination to provide the reader with a text that is thorough and up-to-date, and one of the problems with this book is the shotgun, or smorgasbord effect of trying to cover many topics related by an abstract concept, but not necessarily very similar to each other.
This book consists of sixteen chapters, each one of which deals with a particular cellular phenomenon in which the genetics of DNA is superceded or modified by some other effect. For example, in Chapter Two, the author discusses cell differentiation, why the cells in our body all contain the same DNA but make different tissue types. In Chapter Five, the author discusses, “Why Aren’t Identical Twins Actually Identical.” She points out that identical twins, who have exactly the same DNA sequences in their chromosomes, are not necessarily concordant for genetic diseases such as schizophrenia. She reminds us that the DNA occurs in a kind of “dampening field,” something like a dimmer switch or a volume dial, which determines whether and how the DNA code gets expressed. In Chapter Six, called, “The Sins of the Fathers,” Carey describes how in some exceptional circumstances, environmental influences can be passed across the generations as if our genes could learn, the kind of thing that Lamarck promoted, and that has generally been disproven by modern genetics, but which occasionally pertains, for example the way starvation during warfare can influence subsequent multiple generations.
In Chapter Eight, “The Battle of the Sexes,” Carey takes us through the remarkably complex stages by which our father’s and our mother’s chromosomes can be coordinated when they form a single new entity. In Chapter Nine, the author discusses the complexity involved with the fact that males have only one X chromosome, while females have two X chromosomes, one of which is a duplicate that therefore needs to be shut off. The silencing of one X chromosome in every cell in every woman, and the asymmetry of chromosomes in every male (who have one X chromosome and one Y chromosome instead of a pair of chromosomes) and the possibility for errors in these mechanisms, opens a pathway to interesting speculation about important social issues, such as the biology of gender, or sexuality, issues which the author chooses to refrain from considering in this cautiously scientific book.
My favorite chapter was Chapter Ten, “The Message is not the Medium,” in which the author does an outstanding job of authoritatively dismissing the widespread, misguided idea that DNA codes for protein, and that DNA which does not code for protein is therefore “junk.” She shocks the reader with the dramatic statement that the complexity of living organisms correlates better with the percentage of the genome that does not code for protein than the percent that does. Organisms become more complex, evolving from bacteria, through mice, through humans, not by creating more proteins, but by regulating proteins with greater complexity. At a certain evolutionary point, proteins have become refined, and mutually fitted to the extent that few modifications to them can become adaptive. At this junction, most protein modifications create errors and problems; therefore, from this evolutionary point onward, for organisms to adapt and evolve, few future changes in protein structure can be made, and instead, the way in which proteins can be regulated becomes a new avenue of selection and adaptation.
Carey guides us through detailed descriptions about how the genome is regulated through various methods, such as methylation, acetylation, histone changes, and most remarkably, the way that DNA codes non-coding RNA, which in turn regulates DNA. DNA itself creates RNA molecules that act like dial-turners or button pushers, augmenting or reducing DNA expression. Only two percent of the human genome codes for the manufacture of protein. “The fact that ninety-eight percent of the human genome does not code for protein suggests that there has been a huge evolutionary investment in the development of complicated non-coding RNA-mediated regulatory processes…Complicated networks of molecules influence how, when and to what degree proteins are expressed.”
Another example of Nessa Carey’s carefully documented, stereotype-busting writing, is her emphasis that, “Cancer is not a one-off event. Cancer is a multi-step process.” She points out that women who inherit a mutated BRCA1 gene, are at high risk for breast cancer, but do not necessarily get cancer because other defects have to accumulate as well. We are reminded that cancer is not an entity, but a compounding of replication errors, environmental assaults, viral parasites in nucleic acid, and unbalanced patterns within our inbuilt flexibility systems that are intended to give varying permissions to stem cells’ full potentials. Much of our life is not driven, but poised, and its regulators are multiple.
The thing I enjoyed most about The Epigenetics Revolution was Nessa Carey’s uncompromising attitude towards the complexity, multiplicity, and unexpectedness within the mechanisms that regulate genes. What I enjoyed least about this book is the attempt to cover too many topics, some of them only tangentially related to others. This book has useful charts, illustrations, and meaningful cartoons. Another excellent feature of the author’s style is the emphasis on science as a living and personal process. The book recounts many experiments and counter-experiments and familiarizes us with the human side of scientific dialogue and argument.
This book is more interesting than pleasant, more arduous than easy, and it is not for the average reader, but I constantly felt like cheering for the excellence of Nessa Carey who is so determined to bring to our attention the wonder of genetic inventiveness within our life.
Review by Paul R. Fleischman author or Wonder: When and Why the World Appears Radiant
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cclue
A fascinating read and glimpse into the future of medicine
Reviewed in Canada on February 2, 2023
Octavio F Torres Chazaro
Extraordinario, interesantisimo, bien documentado. Uno de mis favoritos
Reviewed in Mexico on December 28, 2019