Tempering the genetic revolutionLEUVEN, Belgium - We may not be fully aware of it, but future generations will likely consider our era truly historic. Never before has mankind been able to understand the functioning of cells, tissues, and organs, the precise molecular mechanisms of evolution, and where and how our species originated and spread throughout the world.
The technology that allows us to unravel cellular and subcellular processes and mechanisms, identify the causes of diseases and develop more specific and effective treatments, and determine who is biologically related to us and to what degree combines knowledge from biology, computer sciences, information technology, and material sciences. As might be expected, such a revolution in knowledge must also have a significant societal impact, requiring answers to questions that, until recently, were considered pure science fiction.
Today, it is technically possible to sequence the 2.4 meters (7.9 feet) of DNA - present in the nucleus of every cell of our body - in only a few days. And, just as the speed of reliable sequencing continues to increase, the price of sequencing has dropped precipitously, and will soon amount to just a few hundred dollars. Once the function of every fragment of DNA is known, nothing will stand in the way of routine sequencing.
Already, variations in the composition of about 500,000 DNA building blocks (SNPs, or Single Nucleotide Polymorphisms), spread over the total length of the DNA and shown to correlate with particular physical and behavioral characteristics or susceptibility to diseases, are being analyzed routinely. Major errors in DNA composition that are responsible for about 3,000 of the 7,000 known genetic diseases can be visualized, and efforts are underway to identify the causes of the remaining 4,000.
Meanwhile, a growing number of companies are offering a new commercial service: direct-to-consumer analysis of DNA for genealogical or medical purposes. While their activities and clientele are steadily increasing, many of the results currently are of only limited value for determining physical and behavioral characteristics or risks of common diseases such as hypertension, cardiovascular diseases, diabetes, and depression.
Some people, however, claim the right to know all information pertaining to them, including even the slightest elevated risk for these diseases. Some are even willing to undergo preventive measures or modify their behavior to decrease or control this risk. Others must cope with results showing that they carry defects that significantly increase their risk of developing a hereditary form of cancer or dementia, or of transmitting a defect to their children that could, in turn, cause a serious defect in their grandchildren.
Some people - so far still a minority - are fascinated by this new knowledge, and take the results for granted. But more research is needed before we can understand the results of sequencing correctly and apply this knowledge appropriately in risk calculations. For example, more than 97 percent of our DNA contains no information for the synthesis of proteins - that is, it contains no genes - but nonetheless interacts with our genes to increase, decrease, or inhibit the production of proteins.
We also know that even if our DNA is somewhat responsible for increased risks for common diseases, and in some cases is fully responsible for inherited diseases, the environment in which this DNA functions can be as important as the composition of the DNA itself. Indeed, from fertilization on, the environment in which the fertilized egg develops - for example, what the mother eats, whether she smokes or drinks alcohol, and whether she develops diseases or infections - places so-called epigenetic marks on the DNA or on the proteins surrounding it, affecting its function.
This conditioning effect continues and increases after birth, leading to different degrees of epigenetic marking in different organs. Individual differences in susceptibility to diseases can be the consequence. This is nicely illustrated in identical twins, who show as they age increasing differences in the way that their identical DNA is marked by the environment.
Nonetheless, the dangers implied by recent technological progress have become increasingly obvious. For example, it is now possible to analyze the DNA of an unborn child from the blood of its mother and determine its risk for diseases later in life. This opens the way to full-blown eugenics - the selection (by parents, authorities, or others) of children with characteristics considered “appropriate.”
We must take care that we do not become more fascinated by the composition of DNA and what characteristics and risks it carries than we are by the human qualities of less-than-perfect individuals, which we all are. This does not mean that there are no applications of our knowledge that are not important, life-saving, and even necessary. But they are more limited in number and scope than many seem to believe. Now is a time not only to advance current research, but also to reflect and to tread cautiously.
Copyright: Project Syndicate, 2013.
*The author is professor of human genetics at the Center for Human Genetics at the Catholic University of Leuven.
by Jean-Jacques Cassiman