The changing face of the life sciences
IN comparison with its antecedents, contemporary biology presents a dramatically altered image to the world. Not only is it in the process of revolutionizing medicine, agriculture and the environmental sciences, it is also calling in question, through the epic adventure of modern genetics, the very nature of the species homo sapiens. We are far from the poetic reveries of Jean-Jacques Rousseau's botanizing "Solitary Walker", or the attempts of nineteenth-century comparatists to determine the laws of evolution. Biology has been transmuted into an exact, computerized, strangely disturbing science which has spawned marketable technologies that are profoundly modifying the industrial scene and the balance between the industrialized and the developing countries.
The decisive turning point was reached in 1973, the year which saw the birth of the new and revolutionary discipline of genetic engineering, which derived directly from molecular biology. For the first time, the general public became truly aware that the life sciences existed and were capable of exciting a degree of passionate concern rivalling that aroused by nuclear physics.
Political and industrial decision-makers were quick to recognize the birth of a modern technology and to perceive the important practical consequences it could be expected to have on the overall economic equilibrium of the planet. From being primarily a "contemplative" science, biology has become an active, manipulative science, and even at times, unfortunately, a target for speculators.
At this point I would like to give a few examples of some of the most significant achievements of contemporary biology.
. Mapping the human genome
In addition to making it possible to control at will the biosynthesizing capabilities of unicellular organisms, genetic engineering techniques have led to the development of marker devices known as "genetic probes". It is now possible to envisage the use of these probes to draw up an accurate map of the human genetic make-up. Using recombinant-DNA technology(1), scientists have succeeded in cloning(2) fragments, varying in size, of chromosomes taken from human or animal cells within the cells of micro-organisms.
The micro-organisms propagate and amplify these chromosome fragments which can then be sorted and purified. Once they are available in sufficient quantity to be analysed, they can be subjected to two further operations. The first of these, known as physical mapping (or restriction-enzyme mapping) consists of identifying the fragments by studying the manner in which they are cleaved by a battery of restriction enzymes.(3) The second, known as sequencing, consists of determining their chemical sequence, that is, the order in which their constituent elements are linked together.
Before the advent of genetic engineering the existence of genes could only be inferred from the consequences of mutations of which they are the site. Evidence for hereditary traits was found by studying change in an eye pigment, in the morphology of a limb, the behaviour of an animal, or in susceptibility to a given disease. Once tracked down, as it were, its site in the chromosome was usually deduced from studies of crossing based on the frequency of liaison or segregation of characteristics during the recombination of parental chromosomes. Finally, it was possible, under favourable conditions, to reveal certain alterations in chromosomes (splitting, transposition, amplification) by observation using optical or electronic microscopes.
Genetic engineering has made it possible to "materialize" the gene. Representing little more than a millionth part of man's physical inheritance, the gene can henceforth be isolated as a molecule; it has become, technically speaking, "workable". Not only can it be analysed, it can also be manipulated and, thanks to restriction enzymes, be subjected to micro-surgery. …