A team of scientists at the Harvard Medical School has succeeded in isolating a single gene-the basic unit of heredity.
This new technique will allow geneticists to study the detailed operation of a single gene without chemical interference from neighboring genes. It may also encourage the development of genetic engineering-the artificial control of animal and plant characteristics by manipulating genes.
The three researchers, lead by Jonathan Beckwith, associate professor of Bacteriology and Immunology, have expressed strong reservations about their achievement's potential uses.
"The only reason the news was released to the press was to emphasize its negative aspects," said Lawrence Eron, a third-year medical school student. Eron, Beckwith, and James Shapiro, a post-doctoral fellow at the Medical School, carried out the experiment during two months of last summer.
"We did this work for scientific reasons," Eron said yesterday. "It was fun to do-cute tricks and all that. But the more we think about it, the consequences of our work seem frightening rather than beneficial."
"You could surely inject genes for sterility to eliminate undesirables like black people and effete snobs. This could be done simply by injecting viruses containing a sterility gene into the Roxbury or Cambridge water supplies," he added.
"It might also be possible for people like our present administration to use this technique in the distant future to eliminate dissent by injecting genes for more placid behaviour. This would be analagous to Hitler's actions, although it might be called a 'more humane way.' "
The researchers isolated one of the 3000 genes that control a common bacteria called Escherichia coli ( E. coli ). Large numbers of this bacteria live in the intestines of humans and other animals and aid in digestion.
"There are still a lot of steps between isolating a bacterial gene and genetic engineering" in a complex organism, Beck-with said yesterday. "But it is much closer than many people realize."
Genetic information is contained in the long strands of a molecule called deoxyribonucleic acid (DNA). The three Med School researchers isolated a small section of E. Coli DNA that controls the bacteria's ability to use a sugar called lactose.
To extract this gene, the scientists took advantage of the fact that when a virus infects a bacterium it sometimes removes a piece of the bacterium's DNA. They infected E. coli with two types of viruses that were specifically bred to remove the lactose gene from E. coli.
The DNA in these viruses is arranged in two, loosely linked strands, with one molecular strand containing the chemical complement of the other. These long molecules are ordinarily coiled around each other in the head of a virus particle once it leaves the host cell.
After isolating the viruses from E. coli, the scientists chemically separated each of the strands of DNA in thetwo virus strains.
They then combined a single piece of DNA from one virus with another strand from the other virus type.
The lactose gene segments of DNA were chemically complementary and combined easily into a double strand.
But since the two types of viral DNA were not oriented in complementary pairs, the viral DNA remained as loose, single strands.
By treating the DNA with a special enzyme that dissolves single-stranded DNA but does not effect double strands, the three researchers were able to separate the bacteria's lactose gene from the virus.
Bacterial viruses are much better understood than the more complex animal viruses, but this same basic technique of using viruses as gene retrievers may eventually be used in higher animals, Beckwith said.