Human Genetics and Reproduction Part 3

About the development of science in the fields of genetics and reproduction. This part focuses specifically on genetic engineering and cloning.


Nor is that all, for there is a technique that bypasses sex altogether. The British biologist J. B. S. Haldane studied the process, known as cloning, and provided the basic theory way back in the 1930s. Each cell in a person's body--sex cells excepted--contains within its nucleus all the genetic information to create the person's identical twin, or triplicate, or quadruplicate, or quintuplicate, or . . . Such replication is achieved by replacing an egg cell's nucleus with an ordinary body cell nucleus. Once inside the egg, the body cell nucleus acts just like a nucleus freshly formed by the union of sperm and egg. It initiates division and growth that culminate in an identical copy of the individual whose body cell provided the nucleus.

Thus far, the most advanced laboratory clones have been frogs and salamanders. Human laboratory clones are just as possible; we don't see them because biologists refrain from creating them. The thought of human clones tingles along the spine; yet all of us have met clones, some of us are clones, and many of us have created or eaten clones. Identical twins, triplets, and so on began as a single primitive embryo that broke into two or more genetically identical fragments early on; each fragment then developed into a separate individual, creating a natural clone. Farmers commonly graft cuttings from a desirable plant to replicate it. A classic example is the navel orange, which originated as a mutant branch on a missionary's tree in Bahia, Brazil, over 100 years ago. Today this seedless fruit is grown on millions of trees, all cloned from that original branch.

All these techniques work with natural genes, units of inheritance that have appeared over millions of years of evolution. This genetic information is recorded in the structure of DNA, an extremely long molecule that forms the core of each of our chromosomes, the repositories of our genetic inheritance. Over the past 20 years, molecular biologists have taken the initial steps toward understanding the way genetic information is recorded on DNA. Dr. Har Gobind Khorana, a Nobel Prize-winning leader in this field, announced in 1970 that his MIT laboratory team had completed the first artificial copy of an existing gene. By 1976 they had built a gene of their own invention.

Though construction of artificial genes--genetic engineering--is only in its infancy, its potential is enormous. Right now, molecular biologists can produce custom-made bacteria as deadly as diphtheria or botulism, impervious to antibiotics, and easily capable of penetrating our body defenses. Or they can improve the useful strains of bacteria that ferment our wines, brew our liquors, leaven our bread, manufacture our wonder drugs, culture our cheeses. Dr. Ananda M. Chakrabarty of G.E. labs in Schenectady, N.Y., has begun custom-building beneficial bacteria. His first model, just patented, converts spilled oil to healthy nutrients for marine organisms. He has others on the boards that will concentrate precious metals like gold, uranium, or platinum from poor ores; still others will transform organic wastes into petroleum. The potential benefits are endless--and strange, for they'll ultimately include custom-made plants and animals.

In an effort to banish the nightmares from genetic engineering, nearly 100 eminent geneticists and molecular biologists met in California in February, 1975. They agreed on some admirable self-restraints: raising laboratory safety standards to minimize the threat of some new disease escaping; not creating bacteria resistant to antibiotics or natural toxins; and not plugging cancer-causing or other serious disease capabilities into bacteria normally accepted by our bodies. The last restriction would halt experiments that proposed installing SV-40, a virus particle that causes cancer in monkeys, into Escherichia coli, one of our essential intestinal bacteria, because the result could be a cancer epidemic.

The geneticists and molecular biologists have created a strange new world for us, and they're striving to make it safe. Within the decade we'll be groping through this uncharted territory, trying to avoid unimaginable pitfalls in order to reach undreamed-of goals.

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