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Soundings Genetic modification engenders hope, caution

The alphabet is a code, each letter representing a sound, or “phoneme.” String letters together and you’ve got a word, a sentence, a story.

The story of life is written in code, but using only four “letters” – four small molecules strung, like charms on a bracelet, in long strings of DNA. Groups of “charms” – genes – are read by molecular machines and translated into the cells, tissues and organs of which our bodies are made.

Less than a billionth of an inch across, 5 or 6 feet of DNA is folded into nearly every cell in the body – enough to carry some 3 billion pairs of “charms” – a lot of information.



Nature has been mixing and matching and altering genes for billions of years: Life evolves. Farmers have also mixed and matched the genes of animals and plants through selective breeding (It was the farmers’ ability to select for valuable traits that led Darwin to deduce that nature does the same thing, what he called “natural selection.”)

In 1970, scientists discovered that bacteria could, in self-defense, selectively cut the DNA of invading viruses out of their genomes, and then repair the cut.




By 1973, they’d adopted the technique to cut and paste new genes into bacteria. Since all organisms encode their genomes in DNA, the technique works for all forms of life.

Earlier this week, I attended “Bio 2004,” a huge biotechnology convention in San Francisco. In addition to thousands of men and women involved in biotechnology, the convention was attended by some hundreds of protesters.

Four billion years has been time enough for the four-letter genetic code to evolve incredible complexity; we understand only a tiny fraction of it.

The biotech industry, over the years, has issued a lot of supremely optimistic publicity. But several of the lecture sessions at the convention demonstrated that scientists are well aware that things can go wrong – and have.

In English, some words may be pronounced in several ways (“Lead us to the lead mine!”); a sentence may have several layers of meaning. Then there’s the school-kid prank of embedding a secret message that can only be read by stringing together the first letters of each sentence in a story. Our genes are written with similar subtlety.

Modified genes have escaped. “Transgenes” have gone from corn into a wild relative. We need to keep such relatives genetically unpolluted, not least because we’ll need their genes some day to rescue domestic varieties from disease.

Genetically modified corn, not approved for human consumption, has entered the food supply.

Soybeans engineered to produce a pig vaccine have mixed with feed corn (fortunately caught and destroyed before entering the food chain).

Genetically modified pigs have been stolen and made into sausage.

Adding a human gene to a previously benign mouse virus made a harmless disease deadly for mice.

Genetic modification has created products of undoubted benefit and holds even greater promise. Hydrogen, for instance, is a very clean fuel, but virtually none exists in a pure state on Earth – no one’s ever drilled a well and struck hydrogen.

Directed by DNA, plants extract hydrogen from water whenever the sun shines. But – again, directed by DNA – they use that hydrogen to make sugar. If we could manipulate a plant’s genes to skip the sugar step and release the hydrogen instead, we’d have ourselves a hydrogen well.

The most important message of the protests at Bio 2004 is that, while scientists have discussed the potential dangers of genetic manipulation among themselves, a more public discussion is long overdue.

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Alan Stahler trained as a biologist and is an amateur astronomer. He teaches enrichment classes for children and adults at Sierra Friends Center. His science programs can be heard at noon on alternate Tuesdays on KVMR-FM (89.5).


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