DNA is a molecule that does two things. First, it acts as the hereditary material, which is passed down from generation to generation. Second, it directs, to a considerable extent, the construction of our bodies, telling our cells what kinds of molecules to make and guiding our development from a single-celled zygote to a fully formed adult. These two things are of course connected. The DNA sequences that construct the best bodies are more likely to get passed down to the next generation because well-constructed bodies are more likely to survive and thus to reproduce. This is Darwin’s theory of natural selection stated in the language of DNA.
The story of DNA as hereditary material is well known. We all know that, in the middle of the twentieth century, the American James Watson and the Englishman Francis Crick discovered the double-helix structure of DNA. It is this double helix that makes up our genes. It is this DNA molecule that is packaged into our eggs or sperm and that is inherited by our children, making them resemble us.1
The story of how biologists came to understand the way DNA helps to direct the construction of our bodies is less well known. Somehow our DNA tells our cells how to make hemoglobin, collagen, and thousands of other molecules—and how to make the human form of these molecules, not, say, the cat form, which is slightly different. How does the information that is encoded in our DNA get read by our cells, specifying the structure of the many thousands of different molecules that make us up? This is, roughly speaking, the problem of the genetic code. And this code was cracked during the 1950s and 1960s in some of the most profound and beautiful work in the history of biology.
Matthew Cobb tells this story in his latest book, Life’s Greatest Secret. Cobb, a professor of zoology at the University of Manchester, is a working geneticist. He is also a student of the history of science who has written several previous books on the history of biology. Life’s Greatest Secret is aimed at the general reader who may have only a passing familiarity with biology, much less with the detailed molecular mechanics of how DNA does what it does. The book serves as a useful primer for those interested in the brave new world of genetic intervention made possible by the rise of biotechnology. But Cobb’s book will also be of interest to professional scientists as it recounts events in one of the most transformative periods in the history of science: the rise…
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