Dec 1, 2013

The Splice of Life

Dr. James Watson, left, and Dr. Francis Crick with their 
Nobel Prize-winning model of the DNA molecule
Genetic engineering is the process that inserts genes from one living organism into the cells of another, thereby custom-tailoring them to do work they weren't designed for. For example, thanks to genetic engineering, or recombinant-DNA technique, millions of bacteria are kept busy churning out precious human insulin. Scientists built the micro-factories by slipping the human gene responsible for the creation of insulin into E. coli, a mild-mannered bacterium found in our intestinal tract. So far, genetic engineering has been most successful with microorganisms, plants, mice (whose immune systems have been made to mimic those of human beings), and-Stephen King, take note -- livestock: pigs that gain weight faster, cows that give more milk. Science is still working on the problem of getting genetically altered DNA back into a human cell and, we're told, isn't even close to a solution. Someday, however, we may be able to replace or repair bad genes, like the ones responsible for such diseases as cystic fibrosis, sickle-cell anemia, and perhaps even cancer.

To understand how genetic engineering works, you've got to know about deoxyribonucleic acid, or DNA, three letters even more important than MTV. First, go back to the days when you were a single cell -- a fertilized egg, or embryo, whose nucleus contained forty-six packages called chromosomes, twenty-three from each parent, carrying the coded information for all your inherited characteristics, from hair color to susceptibility to stress to, some would argue, sexual orientation and propensity for violence. As your cells divided, each new cell was issued forty-six identical chromosomes (except for your reproductive cells, which, in anticipation of future mating, have only twenty-three apiece).The strand-like chromosomes are made up of several thousand genes, each responsible for a particular trait. And the genes are composed of DNA, the chemical that runs the show, programming and operating all life processes. All living things have DNA in every cell. (The exception: Some viruses contain only a chemical cousin of DNA called RNA.) Indeed, it has been said that if the instructions coded in one person's DNA were written out, they would fill one thousand encyclopedia-sized volumes. You might want to wait for the movie.

In 1953 Francis Crick and James Watson earned a Nobel Prize for discovering that DNA is shaped like a spiral staircase, the famous double helix. Phosphates and sugars form the railing of the staircase, and pairs of four nitrogen bases in various combinations form the steps-up to about three billion of them in human DNA. The order of the base pairs determines the particular characteristics of any shrub, egret, or stand-up comic.

Twenty years after this discovery, two California researchers, Stanley Cohen and Herbert Boyer, found a way to perform DNA transplants. For example, it was they who turned bacteria into human-insulin factories, removing DNA from a human cell and cutting it with special enzymes at the spot where the needed gene is found. Then, using more enzymes, the human gene was snapped into a plasmid, a strand of extra DNA, found in bacteria. When that bacterium reproduces, it creates millions of copies of itself, each with the new gene. In this way scientists produce not only insulin but growth hormone and cancer-fighting interferon.

There's plenty of controversy and intrigue in the world of genetically altered organisms. In 1985, such an organism was tested for the first time outside the lab--semiofficially. A vaccine made by genetically altering a herpes virus was injected into 250 piglets. The test may have launched a golden age of agriculture - or a regulatory nightmare. What if the gene-altered vaccine goes wild, mutates, affects humans? And, not to slip into anticlimax or anything, will small family farmers be able to afford the new technology? You see the problem: legislators who have a hard time formulating a policy on Haiti set loose on something like this.

Gene splicing is not to be confused with cloning. And don't get genetic engineering mixed up with in-vitro fertilization, the creation of test-tube babies. In that case, an ovum (more likely, several ova, to maximize the chances for success) are removed from the mother, fertilized in a petri dish by sperm from the father, and returned to the mother's womb. Today there are more than a million in-vitro children in the world; in fact, the first, Louise Brown of England, is now all grown up. And the term is unfair: The kid spends only a couple of days in a dish, as an egg 1/25 of an inch in diameter.

In a newer procedure, so called prenatal adoption, a woman needn't even produce her own egg. Rather, the fertilized ova of another woman, who has been artificially inseminated with sperm from the first woman’s mate can be implanted in the womb of the first woman and the resulting fetus carried to term.

Yet another technique allows the freezing of eggs, sperm, and full-fledged embryos for future use. A woman might deposit a fertilized egg, meant to be re-implanted later, once she's sown her wild oats or launched her career. Or she could rent a womb, paying someone else to carry her child.

But mightn't that lead to the creation of a class of drone-moms, employed by people who want to buy their way out of morning sickness? Ah, that's just one of the ethical problems of biotechnology, the blanket term for all this fiddling around with Life Itself. Other sticklers: What if the wrong people start tampering with characteristics like physique, building a brave new world of super-jocks and ultra-wimps? What if a genetically engineered microbe escapes from the lab or the test area? There are still some teensy bugs to be worked out. (‘An Incomplete Education’, by Judy Jones and William Wilson)