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The Violinist’s Thumb
Sam Kean
Little, Brown

We hear so much about "genes" and "DNA" that we think we understand genetics. But many of us would have a hard time articulating what these two words actually mean, and how they differ. Early on in his book, The Violinist's Thumb, author Sam Kean artfully lays it out. "A gene," he writes, "is really information – more like a story, with DNA as the language the story is written in. DNA and genes combine to form larger structures called chromosomes, DNA-rich volumes that house most of the genes in living things. Chromosomes in turn reside in the cell nucleus, a library with instructions that run our entire bodies."

The Violinist's Thumb plucks some choice gene stories and, by exploring the language they were written in, the volumes they were collected into and how the libraries' instruction manuals were followed, illuminates how they play out. No small feat.

First, as background, Kean takes us through various points of discovery and reminds us that there was a time when this model – of how we develop, how traits are passed on, how disease might be to some degree predestined – was pooh-poohed. He tells us about Friedrich Miescher, who first discovered DNA in pus, how for a long time no one was very interested in Gregor Mendel's now-iconic work on peas, and how Charles Darwin had a tough time convincing even fellow science types that evolution worked the way he proposed. Later, he also takes us through the Human Genome Project.

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There were many things I learned from reading this book. For instance, I was unaware that there was once a serious effort to create a Humanzee – a hybrid human and chimpanzee. Soviet scientist Ilya Ivanov actually set out to impregnate a female chimp with human sperm. When insemination proved more difficult than he had anticipated, he tried it the other way round – using chimp sperm to inseminate a human female. He had a human female volunteer all lined up when his chimp died of a brain hemorrhage. Before he could try again, he found himself charged with "counterrevolutionary activities" and shipped off to Kazakhstan.

Perhaps my favourite section was about just how much of the human genome is composed of remnants of microbial DNA. There's even a field called "paleovirology," in which scientists study extinct viruses by, for instance, studying their remains in our DNA. In 2006, one French virologist was able to deduce what the original DNA sequence for a particular ex-virus must have been; then he reconstituted it and was able to infect animals with it.

My least favourite bit, however, was just a few pages away. Kean describes, in way too much detail, a couple of Canadian cat hoarders. He insinuates that their desire to house and care for their 689 felines may be related to the fact that two genes in the genome of a parasite, Toxoplasma gondii, which is often transmitted to humans through their cats, may have affected levels of dopamine in the hoarders' brains. I was mildly curious about this claim, so flipped back to the footnote. There he writes: "Scientists have not yet run controlled studies on the correlation between Toxo levels in the brain and hoarding. So it's possible that the link between Toxo, dopamine, cats and hoarding could come to naught." Er, yes. And perhaps that should have been made a little more explicit in the main text.

This book is full of fascinating bits. And Kean is a very good writer. But like so many books these days, it feels more scrapbook than opus. There appears to be little, if any, original reporting. There are no provocative insights. Nor does Kean draw together the import of our genetic code for love, war or genius, as promised. Alas, even the mystery of the violinist's thumb let me down.

Alison Motluk is a science writer based in Toronto.

Some things about DNA you probably didn't know

There's enough DNA in our body to stretch from Pluto to the Sun and back again

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Early estimates were that humans had around 100,000 genes. The real number is somewhere between 20,000 and 25,000.

About 8 per cent of the "human" genome isn't human at all – it's old virus genes.

Craig Venter, one of the fathers of the Human Genome Project, has long stretches of DNA not normally found in humans but not unusual in chimps.

One genetic disorder, dubbed "immigration delay disease," prevents the whorls and grooves of fingerprints from forming.

Breastfeeding activates dozens of genes in nursing infants, both in the intestine and the brain.

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