T.J. Kirkpatrick for The New York Times
Genome Elements of human genome projected onto a model at the Smithsonian’s Natural History Museum.
WASHINGTON — It has been a decade since the human genome was first sequenced and the 3.2 billion rungs of our DNA ladder laid out for analysis.
That achievement — mapping the fundamental biological code that defines our species and characterizes us as individuals — may have implications as important as the splitting of the atom or the discovery of the wheel. We can already envision custom-designed medicines as well as custom-designed fetuses. There are ethical questions to be asked and scientific questions to be answered. And nothing about the subject is simple.
But credit “Genome: Unlocking Life’s Code,” an exhibition at the Smithsonian National Museum of Natural History here that opened in June, with being a bit of a pioneer in its own realm. It is smart, playful, and, while leaning toward the pop-science end of things, enlightening. It gives a sense of what the Human Genome Project was all about, provides glimpses of its promises and hints of its limitations, raises questions about things unknown and suggests questions whose answers we may choose not to know.
The show was created in an unusual collaboration between the Smithsonian and the National Human Genome Research Institute at the National Institutes of Health, and vetted by a board of genetic scientists. The main frustration is that given the immensity of its subject, the exhibition is too modest in size — about 4,400 square feet. It feels overly compressed, particularly in the space allowed for a crash video course in genetics — partly, perhaps, because it is designed to travel to other museums after it closes here. It may even be too successful; crowds on a recent weekday caused bottlenecks at displays and interactive screens.
The exhibition also casts a wide age net, and generally succeeds, mostly by using interactive technology and providing small bits of information at a time, as if it were carefully replicating a strand of its DNA for the visitor. Interactive screens can become laborious as you formulaically click through them, but lessons are clearly communicated.
Life, in all its complexity, we are reminded at the beginning, is based upon almost elementary information: four symbols — the A, C, G and T that stand for DNA’s nucleic acids — and the order in which they appear in the genome. That might seem trivial, but the amount of data is immense. If you typed 360 letters a minute, eight hours a day, we are told, it would take nearly a hundred years to type out the letters mapping the human genome. A video screen here is scrolling fast through that roster; it will take a year to complete. Yet all that information is compressed into each human cell.
Once it became possible to examine that code and specify its sequence, variations could be identified, comparisons made, changes traced. And a similar procedure could be used throughout the natural world. We are just beginning to glimpse the consequences.
In a section about genetic research in animals, for example, viewers manipulate cursors on a large display examining a “tree” of related creatures. Horseshoe crabs have not changed their shape in 200 million years; are they, then, we are asked, living fossils, ancient creatures living in the present? No. Though the genes determining their shape have remained relatively unchanged, other genes have been transformed through long evolutionary processes.
Examine “naked mole rats” — something you probably wouldn’t consider outside of the display — and you find that they live 30 years, feel no pain and don’t get cancer. Why? Their cells remove damaged proteins more efficiently than ours. Genomic research may suggest how to apply similar processes in human medicine.
Another interactive display, “Explore your genes!” presents a human figure on screen with bodily “hot spots”: when clicked on, associated traits or diseases appear — hair color, mental illness, taste sensitivities, sickle cell anemia — along with information about the genes controlling them. Genes have been linked to trivial traits. (“Did you know some people have wet earwax and some people have dry?”) And some 4,000 diseases are caused by single flaws in human genes.
Genomic research doesn’t just identify the source of a disease or trait, though; it also has helped discover remedies. Short videos present miniature case histories. Perhaps the most powerful example shows twins who, as children, were thought to have cerebral palsy. Once it was shown that they were actually afflicted with genetically caused Segawa’s dystonia, proper medication almost miraculously eliminated the symptoms.
Obtaining this level of genetic information is no longer a highly rarefied procedure. The Human Genome Project required eight years, more than $2.7 billion and international cooperation. The cost of sequencing a genome is swiftly dropping, we learn, and “soon it will cost $1,000 or less.” You can now get a partial analysis of your genome in a few weeks for less than a hundred dollars.
So questions are asked that would have been abstract a decade ago: What do you want to know and why? One interactive display introduces us to fictional characters of varied ages who decide whether to get genetic testing and then decide how to act on the information. In one example, Maya wants to become a concert pianist, but genetic tests show a 30 percent risk of rheumatoid arthritis, which would cripple her career. Should that affect her choices?
Another display poses ethical or policy questions. Should health insurers be permitted to set rates based on genomic information? Should genomic discrimination ever be permitted? Are there questions genomic scientists should not be allowed to study? Each question offers you a choice of yes, no or maybe, and a rationale; you then see how visitors voted before you. (Should there be limits on genomic research? At the time of my visit, 46 percent said no.)
The possibilities and problems are astonishing. Yet we stand now only at the beginning of a transformation in human self-knowledge. Vast regions of the genome are not fully understood. And what is the nature of genetic complexity anyway, when, we are told here, amoeba have 670 billion bits of information (“base pairs”) in their genome compared with humans’ 3.2 billion. Even barley surpasses us, with more than 5 billion.
What actually matters in these long strings of data: 99.9 percent of each person’s genome is exactly the same as everybody else’s; our individuality hangs on only .1 percent.
So much is happening in this field, it would have been helpful if a final section had been devoted to examining where research is going. And beyond a streaming news ticker above one display, it would also help to see frequently updated surveys of recent genomic news in some detail. In June, for example, a Supreme Court decision barred patents on human genes; this month we read of a decision by the National Institutes of Health that gave descendants of Henrietta Lacks — from whom medically important HeLa cells derived — some involvement with the continuing exploration of her genome.
But the cumulative effect is to inspire amazement about how much has happened in the last decade, how matter of factly we now seem to take it, and how much more is yet to come. And there is some reassurance that while we are each perishable, as one introductory film tells us, “your DNA can last for 100,000 years, if you don’t get cremated.”
댓글 없음:
댓글 쓰기