Table of Contents:
- a. Friedrich Miescher and the Discovery of DNA
- b. Gregor Johann Mendel and the Basics of Heredity
- a. From Mendel to Morgan
- b. Thomas Hunt Morgan: Chromosome Theory, Genetic Heredity & The Modern Evolutionary Synthesis
- a. How Genes Become Traits
- b. Junk DNA
- c. Mutations
- a. Life Begins
- b. From Simple Microbes to Single-Celled Organisms with Internal Complexity
- a. An Introduction to Multi-Celled, Complex Organisms
- b. Human Complexity
- c. Monstrous Mutations
- a. Primate Beginnings
- b. Humanzees
- a. An Introduction to the HGP
- b. The Discoveries of the HGP
In a sense the story of DNA has two strands. On the one hand, as the blueprint of all that lives and the mechanism of heredity, DNA tells the story of life (and the history of life), from the smallest, simplest microbe, to we human beings, who have managed to figure all of this out. Of course, there is still much about DNA that we don’t know. But given that we didn’t even know of its existence until a lowly Swiss physician and biologist named Friedrich Miescher stumbled upon it in the 1860’s, you have to admit we’ve come a long way in such a short time. And this is just where the second strand of the story of DNA begins: the story of our unraveling the mystery. While perhaps not as grandiose as the story of life itself, this detective story is significant in its own right, for it has transformed how we understand all that lives—including ourselves. This is especially the case given that the latest chapters in this story have revealed not only our own genomic blueprint, but the (deeply daunting) fact that we have the power to change this blueprint and thus became the masters of our own future as a species. While each of the strands of the story of DNA could fill a book in their own right (if not several), the author Sam Kean has managed to weave the two together and fit them both in his new book The Violinist’s Thumb: And Other Lost Tales of Love, War and Genius, as Written by Our Genetic Code. Kean’s project may seem like a particularly tall task, but he manages to pull it off by way of focusing in on only the main (and/or juiciest) moments and characters throughout.
Kean divides his tome into four parts. The first part explores the basics of DNA and heredity, and the earliest discoveries thereof. Here we are introduced to the aforementioned Miescher, as well as Gregor Mendel, who teased out the basic laws of heredity using his famed peas. We also learn of Thomas Hunt Morgan and his team of eccentric lab assistants who managed to marry Mendelism (genetics) with Darwinism (evolution by natural selection) to develop the modern evolutionary synthesis, which stands as the main pillar of modern biology. We also learn about genetic mutations and how these glitches are the key to evolution. Sadly, these glitches also have their downside, which we witness through the story of Tsutomu Yamaguchi, who had the terrible misfortune of being in the blast zone of both of the nuclear bombs that the US dropped on Japan at the end of WWII.
Part II of the book explores DNA’s role in the beginnings and evolution of life. In particular, Kean focuses on the major leaps in evolution, from the first microbes, to microbes with complex internal specialization, to multi-celled organisms with specialized cells (which includes all plants and animals), to mammals, to primates, to us. All of this may sound very technical, but Kean manages to keep the story lively with tales of northern seafarers encountering angry polar bears (and learning that biting into their innards can be just as deadly as them biting into yours), and Soviet scientists embarking on a project to create humanzees (yes, that’s a cross between a human and a chimpanzee).
Part III of the book turns to human DNA in particular, and what sets us apart as a species. Here we learn how our DNA reveals that our species has passed through several genetic bottlenecks—meaning there have been numerous occasions where our numbers have dwindled to near-extinction levels, with the latest bottleneck occurring as little as 70,000 years ago. This has left us with far less genetic diversity than most other species, including our closest living relatives, the chimps (compared to whom we also have two less chromosomes). We also learn about some of the genes that have contributed to the evolution of our big brains—the one thing that separates us most as a species. Finally, we learn about the role that DNA plays in our peculiar attraction to art.
The fourth and final part of the book enters into the intricacies of the structure of DNA, and how our unraveling these intricacies (through the work of Watson and Crick, and the Human Genome Project) has allowed us to manipulate life forms. While these discoveries have opened up enormous opportunities, they have also led to some very poignant questions about just how we should be using this knowledge—especially when it comes to ourselves and our own species. As our knowledge of DNA increases (currently at a rate that exceeds Moore’s Law) these questions will only become more pressing moving forward.
What follows is a full executive summary of The Violinist’s Thumb: And Other Lost Tales of Love, War and Genius, as Written by Our Genetic Code by Sam Kean.
a. Friedrich Miescher and the Discovery of DNA
Deoxyribonucleic acid (DNA) was first discovered in the 1860’s by a Swiss physician and biologist named Friedrich Miescher. At the time that Miescher made his discovery he was working at a lab in Turbingen, Germany, as the understudy of a biochemist named Felix Hoppe-Syler (loc. 205). Hoppe-Seyler had been studying human blood cells, and was working to catalog all of the chemicals found therein. As he was focussing on red blood cells himself, Hoppe-Seyler sloughed off white blood cells to his understudy. As it turns out, red blood cells do not have nuclei, which is where DNA is found, whereas white blood cells do (loc. 201), so in effect, by sloughing off white blood cells to his understudy, Hoppe-Seyler was sloughing off one of the biggest discoveries in scientific history.
Miescher discovered DNA in a roundabout way, by first isolating the nuclei of his white blood cells (extracted from the pus-filled bandages from a local hospital), then charring the resulting paste to determine its chemical composition (after it had, bafflingly, resisted protein digestion—indicating that it wasn’t in fact a protein [loc. 223]). Miescher’s chemical analysis revealed a new and unknown substance: DNA (loc. 226).
Unfortunately, Miescher’s mentor wasn’t all that impressed, as he was convinced that his understudy has made a mistake in his analysis (loc. 229). Nevertheless, two years of follow-up work revealed that Miescher had in fact discovered a new, and non-proteinous, substance (loc. 233). Still though, no one had any idea what DNA did, so Miescher’s discovery caused hardly a ripple of excitement. In fact, Miescher’s discovery was half mocked by his own mentor, who “insisted on writing a patronizing editorial to accompany Miescher’s paper, in which he backhandedly praised Miescher for ‘enchanc[ing] our understanding… of pus” (loc. 233).
b. Gregor Johann Mendel and the Basics of Heredity
A crucial piece of the puzzle in understanding the role of DNA is understanding heredity (and the notion of genes), and right around the same time that Miescher was discovering DNA, in a monastery not 400 miles from Miescher’s lab, worked a science-minded monk who was making great strides in doing just this (loc. 142) The monastery was called St. Thomas, and the monk was one Gregor Mendel. (In fact, it turns out that Mendel was quite a bit more science-minded than monk-minded, as “by his own admission, Mendel became an Augustinian friar not because of any pious impulse but because his order would pay his bills, including college tuition” [loc. 280]). The Abbot at St. Thomas had encouraged Mendel (a graduate of the University of Vienna) to study agriculture, with the hope that he might be able to increase productive yields (in order to help the monastery extricate itself from its mounting debt) (loc. 283). Lucky for Mendel, the study of agriculture would lead him to a few very important discoveries indeed.
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