Sunday, July 4, 2010

The Secret of Life

DNA: The Secret of Life by James D. Watson (with Andrew Berry). Alfred A. Knopf,

The News & Observer

May 5, 2003

The Genes Scene

By Phillip Manning

Half a century ago, James D. Watson and Francis Crick unraveled the structure of a molecule that Crick said contained the "the secret of life." That molecule was deoxyribonucleic acid or DNA, and determining its structure promised to be one of those rare events in science: a discovery that has far-reaching practical consequences (such as the
invention of the transistor) and that tells us about ourselves and our world (such as Darwin's theory of evolution). Has the DNA revolution lived up to its billing?

That is the question Watson addresses in "DNA: The Secret of Life," and he is perfectly positioned to answer it. Watson, along with Crick and Maurice Wilkins, won a Nobel Prize in 1962 for discovering the double helix, and he has been a prominent figure in DNA-related science for 50 years. In this richly illustrated book, he describes the tremendous progress achieved by molecular biologists during that time.

He starts with the discovery itself, the structure of DNA, the Holy Grail of 1950s biology, which enabled scientists to understand how genetic information is stored and replicated. This understanding has profoundly transformed our world: genetically modified foods are on our tables; DNA "fingerprinting" is the gold standard for identifying criminals and exonerating the innocent; and the genes causing many inherited diseases - such as Huntington and Tay-Sachs - have been identified. In case after case, Watson explains the science that made these advances possible and enlivens his message with tales about the
scientists who participated in the revolution.

Take, for example, the chapter on the early days of recombinant DNA - the process that allows scientists to isolate and copy genes. Watson explains clearly the science behind the process, which he calls "cutting, pasting, and copying." Restriction enzymes cut a strand of DNA, isolating a desired gene. Ligase then glues the ends of the gene together forming a circular strand of DNA called a plasmid. The plasmid is inserted into a bacterium, which then goes about its usual business of reproducing itself and the plasmid. Thus, a single DNA molecule can produce enormous quantities of a gene. And since genes make proteins, the workhorses of all cells, scientists could potentially clone any
amount of any protein they desired.

That Herb Boyer and Stanley Cohen worked out this cloning technique is a matter of record. But who besides Watson would know that they thrashed out the details in a Waikiki deli. Or that Boyer was so enamored with DNA that he named his Siamese cats Crick and Watson. Later Boyer and another partner plunked down $500 and started the first biotech company. They named it Genentech, and its first product was human insulin. This development was a godsend to 8 million diabetics in the United States who previously had to control their disease with pig or cow insulin, which can cause allergic reactions. This is exciting stuff: a beneficial and practical use of technology that came directly out of scientists
newfound understanding of the double helix.

Another consequence of the DNA revolution was the sequencing of the human genome. The genome provides us with a portrait of our species; all that we are derives from the order of the 3.1 billion base pairs in the DNA that resides in almost every cell in our bodies. DNA analysis can also identify our closest relatives. Mary-Claire King and Allan Wilson compared the human genome with that of the chimpanzee and showed that the DNA sequences between the two species differ by a mere 1 percent. DNA sequencing can also provide historical insights. Another analysis led molecular biologists to conclude that the human lineage separated from the great apes about 5 million years ago, overturning paleontologists' long-held belief that the split occurred 25 million
years ago.

But molecular biology sheds light on questions that go back much further than a few million years. In fact, DNA technology has raised questions about - and possibly found answers to - the origin of life itself. Most DNA is found in the nucleus of a cell. Soon after Watson and Crick determined the structure of DNA, scientists found that although DNA provided the template that governed the life of the cell, its cousin ribonucleic acid (RNA) had the crucial role of ferrying DNA's instructions out into the body of the cell where proteins are assembled. But why do we need RNA? Why doesn't the cell simply make proteins in the nucleus? Francis Crick believes he has the answer: life (or at least genetic replication) started with RNA. DNA, which is a more stable molecule and better for long-term storage of genetic information, came later. This neatly answers the question of why modern cells depend on RNA for vital functions: it was there first, and natural selection put it to good use.

Watson's book, however, is more than a superb history of 50 years of DNA. Watson is the rare combination of a good writer and good scientist. His first book "The Double Helix," was a lively, first-hand account of the discovery of the structure of DNA. It was a best seller, despite the objections of feminists, who thought his portrayal of Maurice Wilkins's coworker Rosalind Franklin was unflattering and unfair. The tone of this book is more subdued, perhaps because Watson is older now and was assisted by a coauthor, Andrew Berry. But neither age nor coauthor can tame Watson completely, and flashes of the brash, outspoken 25-year-old shine through.

Consider his views on genetically modified (GM) foods, which are made from crops that carry a gene inserted in the plant's DNA. One famous example is Bt corn, in which scientists have introduced a gene that produces a toxin that kills insects, eliminating the need for pesticides. Although the taste of Bt corn is indistinguishable from ordinary corn, it scared consumers, especially in Europe where it was labeled "Frankenfood." Even Prince Charles weighed in on the issue, pronouncing that "this kind of genetic modification takes mankind into realms that belong to God."

But Watson will have none of this princely nonsense. "It is nothing less than an absurdity," he writes, "to deprive ourselves of the benefits of GM foods by demonizing them it is nothing less than a crime to be governed by the irrational suppositions of Prince Charles and others." Indeed, the greatest benefit of the DNA revolution may not be its material benefits. Like all great scientific advances, it is helping us beat back the shadows of superstition with knowledge.