Martin Henry WHOSE CHILD is it? Who committed this crime? DNA testing now provides almost 100 per cent foolproof answers to these questions and other questions of identity, as long as samples of body tissue can be obtained. And this is only one application of a mighty genetics revolution which is re-making our world and placing in human hands the tools to re-make ourselves.
The revolution began in a laboratory at Cambridge University with a group of young men chasing the secrets of inheritance. Francis Crick, James Watson and Maurice Wilkins wanted to identify the molecular stuff of inheritance. On February 28, 1953, the now famous double helix molecule of DNA was unveiled to the world. Fifty dramatic years in what humankind has been able to do with genes have passed.
Actually, in the nature of scientific discoveries, the DNA revolution began long before 1953. For all of history, humans have noted that offspring resemble parents but are not facsimilies or identical copies. The curious would have wondered why. For most, it was simply a fact of life. The observed knowledge of resemblances was exploited in plant and animal breeding to generate varieties with combinations of desired traits. Around the same time that the fellows at Cambridge were figuring out the structure of DNA, on the local scene, Thomas Lecky was applying the age-old techniques of animal breeding, combined with the existing knowledge of genetics, to produce varieties of cattle with desirable features for the tropics. Last year the 50th anniversary of his Jamaica Hope breed was celebrated.
Experimenting with peas in his monastery garden in the Austrian town of Brunn, the celibate monk Gregor Mendel, curious about inheritance, became the Father of Genetics some 90 years before the double helix discovery. [Brunn is now Brno in the Czech Republic, as European borders skip about]. Mendel, the bean counter, patiently cross-bred peas having different characteristics and worked out the fundamental laws of inheritance.
But Father Mendel couldn't figure out how those laws worked. The search was on for the "factors of inheritance" which were soon called "genes" in scientific shorthand. The story is as fascinating as any Sherlock Holmes plot!
The story runs along the following lines, briefly: When organisms sexually reproduce only the sex cells get from parent to offspring, so, clue number one, the factors of inheritance must be in the sex cells. But where in those cells, and what? Microscopic techniques showed that the nuclei of the sex cells fused during reproduction. [First observed in sea urchins!] So the factors were in the nucleus, then.
A little later, chromosomes in the nuclei were caught red-handed behaving in exactly the same manner that Mendel's factors were expected to behave for the laws of genetics to work. "Chromosomes" literally means coloured bodies. They are brightly staining, thread-like bodies in the nuclei of nearly all cells and are particularly obvious under microscopes when cells are in the act of producing new ones by division.
There are few chromosomes occurring in pairs and thousands of inherited factors, so obviously there must be many factors strung on a single chromosome, my dear Mr. Watson. And those factors are paired in the pairs of chromosomes, the pairs separating when the sex cells are formed otherwise there could be no mixing of factors from two parents, and successive generations would have more and more chromosomes accumulating in cells. Clearly an impossibility!
At first people thought that it was the nuclear chromosomal proteins that carry the genetic code. But, for good experimental reasons, suspicion shifted to a less well known category of molecules, deoxyribose nucleic acid, which everybody now calls DNA for short.
What brought Crick, Watson and Wilkins the Nobel Prize was to go from here to figure out the structure of this genetic molecule. This big molecule encoding all those factors of inheritance is disarmingly simple. Only four code bases are involved in two pairs. A sequence of bases constitute a gene. The paired bases form the cross bars of a ladder, with protein forming the side beams of the ladder. Then God gripped both ends of the DNA ladder and with a sharp twist produced the twisted ladder double helix.
The discovery of the double helix has opened up a floodgate. The technical understanding of gene structure has allowed precise gene manipulation or genetic engineering, and the application of genes to technological solutions in medicine, agriculture, industry, criminology, and everywhere else that living material or the products of living organisms are used.
James Watson was only 24 when he helped launch the Double Helix Revolution. He was tapped to be the first Director of the Human Genome Project with the objective of fully mapping the whole human genetic code of some 30,000+ genes. In high scientific drama, the Government partners in the HGP were publishing on the Internet daily progress updates as the work rolled. Some 18 countries participated alongside private enterprise. In June 2000, the Project announced that the rough draft or the human genome had been completed a year ahead of schedule. Round about now, to mark the 50th anniversary of Double Helix, the work should be completed.
Cutting and splicing genetic material and moving stuff from one species to another have allowed human intervention in the design of organisms on an altogether unprecedented scale. Genetically modified organisms (GMOs) are now patented like any other invention. They are the objects of hope and hype, of fear and protest.
The discovery of the double helix has opened promise and peril on a scale unknown in the history of science. People are talking about the 21st century as "the biology century". James Watson, still vigorous and working as Director of the Cold Spring Harbour Research Laboratory in New York was interviewed by Newsweek for the 50th anniversary. Q: "Are you for genetic manipulation in humans? A: "Eventually. We can already make plants resistant to viruses and we could do the same thing in humans. I don't see anything wrong with it. I mean, we've tried to enhance everything else in our lives."
Martin Henry is a communication specialist.
