Science's Top 10: Genome Sequencing Named Top Scientific Advance Of 2000

Science's Top 10 research advances, chosen for their profound implications for society and the advancement of science, appear in the journal's 22 December 2000 issue.

Genome sequencing steamed full speed ahead this year, as researchers used a synthesis of biology, chemistry, physics, mathematics, computer science, and engineering to decode the script of life in a variety of organisms, from people to fruit flies.

A year ago, reasearchers had completely read the genome of only one multicellular organism, the worm, Caenorhabditis elegans.

Now, sequences exist for the yet-to-be-published human genome, the fruit fly, and the plant geneticists' favorite weed, Arabidopsis thaliana. The genomes of several microbes have been sequenced as well, including those that cause cholera and meningitis. Close on the heels of these successes, the genomes of the mouse, rat, zebrafish, and two species of puffer fish are also nearing completion.

Researchers are already reaping new knowledge from these sequencing efforts, including insights into the diversity of cancer, the causes of aging, and the complexity of the immune system. In the 21st century, researchers will decipher whole families of genes and whole pathways of interactive proteins.

These advances will bring with them a host of ethical questions that we have only begun to address. Yet, genome sequencing's potential for advancing human health and our understanding of life has made its allure irresistible.

Science also salutes nine other scientific achievements of 2000. Except for the first runner up, the others are in no particular order.

RNA Runs the Ribosome: Last year witnessed the unveiling of the first molecular map of the ribosome, the cell's essential protein factory. In 2000, higher-resolution maps of the ribosome revealed startling details about its structure that may boost support for an "RNA world" as the model for the origin of life on Earth. Although the large unit of the ribosome consists of both ribosomal RNA (rRNA) and proteins, researchers found that the "active site" on the ribosome--the site of the chemical reaction that changes genetic information into the beginnings of a protein--contains only rRNA. This suggests that the ribosome is actually a ribozyme, an RNA molecule that can catalyze its own chemical reactions. RNA's starring role of in the ribosome may support the idea that life on Earth began with RNA. Other research in 2000 bolstered support for the ribosome's antiquity, and uncovered mechanisms in the cell that guard against defective protein production.

First Out of Africa: Fossil skulls, some 1.7 million years old and unearthed from the well-dated site of Dmanisi in the Republic of Georgia, may represent the first human ancestors to journey out of Africa. According to their discoverers, the well-dated Dmanisi fossils are the first fossils discovered outside of Africa to show clear signs of African ancestry, and may be linked to the early human species Homo ergaster, the African version of Homo erectus. Relatively unsophisticated "pebble-chopper" stone tools found with the Dmanisi fossils suggest that humans may have ventured out of the African cradle earlier than previously suspected, before the development of a more advanced tool kit that included the hand ax.

Plastic Electronics: This year, electrically conducting plastics formed the basis for a bevy of technological achievements using cheap and versatile organic molecules. Their discovery also won three scientists the Nobel Prize in chemistry. Two of the year's highlights: an array of hundreds of organic computer chip components on flexible plastic (for use someday in flat panel displays, electronic tags, maybe even disposable cell phones), and an organic laser, in which organic "tetracene" molecules emit light when excited by electrical current.

Old Cells, New Tricks: Scientists delivered a decisive blow this year to the once-canonical notion that adult cells are wedded to their identities. In studies with mice and human transplant recipients, adult cells from certain parts of the body re-made themselves into an impressive variety of other cell types. If this identity-switching process can be controlled, healthy adult cells might be useful for repairing tissues damaged by injury or disease. In other manipulations of cell fate during 2000, researchers managed to clone pigs, which might provide a source of transplantable organs. Cloning techniques also produced a fetal guar, an endangered animal from India and southeast Asia, raising hopes for rescuing endangered species.

A Watery Solar System?: The possibility of recent water flow on Mars and further convincing evidence for an ocean on the Jupiter moon Europa made headlines in 2000. High resolution images of the martian surface, captured by the Mars Orbiter Camera (MOC), showed signs of recent groundwater seepage and runoff that may be less than a million years old, and could be flowing still. Other MOC images of possible martian sedimentary rock suggest that the planet may have been a land of lakes during its earliest history. Also this year, data collected by the Galileo spacecraft on Europa's internal magnetic field and its cracked and stretched crust strengthened the case for a salty, global ocean lurking beneath the moon's icy shell. Since many researchers believe that water is essential for the existence of life, these discoveries have piqued interest in the possibility of finding life within our immediate solar neighborhood.

Cosmic BOOMERANG: In 2000, researchers completed the most detailed map to date of the early universe with the help of BOOMERANG and MAXIMA, balloons armed with microwave detectors and sent aloft to probe for fluctuations in the cosmic microwave background, the afterglow of the Big Bang. The map made from these data confirm most scientists' view that the universe is flat (with no curve to space and time), but cast doubt on the current simple models of how much ordinary and dark matter exist in the universe, and how the universe went through its early expansion.

Receptor Roles: Scientists gained new insight into the various roles of nuclear hormone receptors, discovering variants of these cell structures that mediate processes such as cholesterol metabolism and fatty acid production, and implicating others in diseases such as diabetes and certain types of cancer. This year's bumper crop of nuclear hormone receptor discoveries could lead to new targets and treatments for some of these diseases. Researchers also illuminated the crucial effects of the receptor called PXR, which appears to jump-start the body's response to unfamiliar chemicals, and may be involved in drug-drug interactions.

Rendez-Vous with an Asteroid: After circling the asteroid Eros for less than half a year, the NEAR Shoemaker spacecraft revealed that the space rock contains some of the most primitive matter in the solar system. This discovery suggests that Eros, and other asteroids like it, are the long-sought suppliers of the most common meteorites arriving on Earth. For decades astronomers have been unable to find the source of the so-called "ordinary chondrite" meteorites, bits of the unaltered building blocks of the solar system. But Eros's elemental composition, measured as NEAR Shoemaker came closer to the asteroid than any spacecraft has before, turns out to match that of the ordinary chondrites.

Quantum Curiosities: The already-weird world of quantum mechanics got a lot weirder in 2000, as the boundary between the quantum and classical world started to break down. The perplexing idea that objects can have seemingly incompatible properties, such as being in two places at once, has generally been thought to apply only to tiny particles such as electrons. This year, researchers observed this phenomenon on a much larger scale, reporting that an electric current can flow around a superconducting loop of wire in both directions at the same time. And in January, a scientist challenged another long-standing assumption by showing that quantum computers don't need a quantum property called "entanglement" to solve complex problems at lightening speed.

Best Bets for Hot News in 2001: As in previous years, the editors of Science have chosen six hot topics to watch in 2001. This year, their choices include: infectious diseases, ocean studies with satellites, quality control in RNA synthesis, science funding around the world, the post-Big Bang "quark soup," and asymmetry in cell development. The editors also check in on last year's scorecard to see how well they did with their millennial predictions.

Science's Top 10 also includes some other, more dubious, honors. The Meltdown of the Year goes to the federal government's pursuit of Los Alamos physicist Wen Ho Lee. The award for Disappearing Discovery of the Year goes to Archaeoraptor, thought to be a novel combination of bird and dinosaur, but exposed as the combination of two different fossils. In a box on Biomedical Ethics, Science also reviews the fallout from gene therapy f