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Already, the genomes of several individuals have been sequenced, and rapid improvements in sequencing technologies are making the sequencing of "me" a real possibility.

The potential to quantify one’s genetic risk for cancer, asthma, or diabetes — is both exhilarating and terrifying.

It comes not only with great promise for improving health through personalized medicine and understanding our individuality but also with risks for discrimination and loss of privacy.

What is it about the oocyte that rejuvenates the nucleus of a differentiated cell, prompting the genome to return to the embryonic state and form a new individual?

In a series of papers, researchers showed that by adding just a handful of genes to skin cells, they could reprogram those cells to look and act like embryonic stem (ES) cells. ES cells are famous for their potential to become any kind of cell in the body.

In June this year, in two announcements that electrified the stem cell field, a Japanese group, along with two American groups, showed that the iPS cells made from mouse skin could, like ES cells, contribute to chimeric embryos and produce all the body’s cells, including eggs and sperm.

The work convinced most observers that iPS cells were indeed equivalent to ES cells, at least in mice. Then in November came a triumph no one had expected this soon: Not one, but two teams repeated the feat in human cells.

In December, scientists reported that they had already used mouse iPS cells to successfully treat a mouse model of sickle cell anaemia.

What’s smaller than an atom but crashes into Earth with as much energy as a golf ball hitting a fairway? Since the 1960s, that riddle has tantalized physicists studying the highest energy cosmic rays, particles from space that strike the atmosphere with energies 100 million times higher than particle accelerators have reached. This year, the Pierre Auger Observatory in Argentina supplied key clues to determine where in space the interlopers come from.

On their long trips, protons loss their energy and leaves few with more than 60 EeV. So the excess suggested that the rays might be born in our galactic neighbourhood. But researchers with the Hi-Res detector in Dugway, Utah, saw only two 100-EeV rays, about as many as expected from far-off sources.

Last month, the Auger team reported that they seem to emanate from active galactic nuclei (AGNs): enormous black holes in the middles of some galaxies. The AGNs lie within 250 million light-years of Earth, close enough that cosmic radiation would not have drained the particles’ energy en route.

Auger researchers haven’t yet proved that AGNs are the sources of the rays, and no one knows how an AGN might accelerate a proton to such stupendous energies.

Just when some crystallographers were fretting that the task was impossible, researchers nabbed a close-up of adrenaline’s target, the beta 2-adrenergic receptor. Its structure has long been on the to-do list.

The receptor is one of roughly 1000 membrane-spanning molecules called G protein-coupled receptors (GPCRs). By detecting light, odours, and tastes, the receptors clue us in to our surroundings.

From antihistamines to beta blockers, the pharmacopoeia brims with medicines aimed at GPCRs — all of which researchers discovered without the benefit of high-resolution structures. A clear picture of, say, a receptor’s binding site might spur development of more potent, safer drugs. But scientists had cracked only one "easy" GPCR structure, for the visual pigment rhodopsin.

Getting a look at the receptor took the leaders of two overlapping crystallographic teams almost 2 decades. The effort paid off this fall with four papers published in the journals Science, Nature, and Nature Methods.

Sixty years ago, semiconductors were a scientific curiosity. Then researchers tried putting one type of semiconductor up against another, and suddenly we had diodes, transistors, microprocessors, and the whole electronic age. Startling results this year may herald a similar burst of discoveries at the interfaces of a different class of materials: transition metal oxides.

Transition metal oxides first made headlines in 1986 with the Nobel Prize-winning discovery of high-temperature superconductors. Since then, solid-state physicists keep finding unexpected properties in these materials. But the fun should really start when one oxide rubs shoulders with another.

If different oxide crystals are grown in layers with sharp interfaces, the effect of one crystal structure on another can shift the positions of atoms at the interface, alter the population of electrons, and even change how electrons’ charges are distributed around an atom.

Teams have grown together two insulating oxides to produce an interface that conducts like a metal or, in another example, a superconductor.

Theoretical physicists in California recently predicted that semiconductor sandwiches with thin layers of mercury telluride (HgTe) in the middle should exhibit an unusual behavior of their electrons called the quantum spin Hall effect (QSHE). This year, they found just what they were looking for.

The effect is the latest in a series of oddball ways electrons behave when placed in external electric and magnetic fields. In 1980, researchers in Germany and the U.K. discovered one of these anomalies, called the quantum Hall effect.

When they changed the strength of a magnetic field applied perpendicular to charges moving through thin layers of metals or semiconductors, they found that the conductance changed in a stepwise, or quantized, manner.

One upshot was that charges flowed in tiny channels along the edges of the materials with essentially no energy loss. The finding triggered hopes of new families of computer chip devices.

In recent years, theorists have predicted that materials with the right electronic structure should interact with electric fields to result in the QSHE — and a spin-driven version of near-lossless conduction.

Such materials would also do away with the need for high magnetic fields and perhaps even for low temperatures. If researchers can do the same trick at room temperature, the discovery could open the door to new low-power "spintronic" computing devices that manipulate electrons by both charge and spin.

Fresh evidence illuminating how immune cells specialize for immediate or long-term protection had researchers a little feverish this year. When a pathogen attacks, some CD8 T cells become short-lived soldiers, while others morph into memory cells that loiter for decades in case the same interloper tries again. The new work demonstrates how one cell can spawn both cell types.

A T cell remains passive until it meets a dendritic cell carrying specific pathogen molecules. As the cells dally, receptors and other molecules congregate at each end of the T cell. A U.S.-based team tested the proposal that if the T cell then divided, its progeny would inherit different molecules that might steer them onto distinct paths.

In March, the team reported experiments showing that different specialization-controlling proteins amassed at each pole of a T cell during its dance with a dendritic cell. When the researchers nabbed newly divided T cells, they found that progeny that had been adjacent to the dendritic cell carried receptors typical of soldiers, whereas their counterparts showed the molecular signature of memory cells. Unequal divisions could also help generate diversity among CD4 T cells, immune regulators that differentiate into three types. Practical applications of the discovery will have to wait until researchers know more about memory-cell specialization.

Society may finally be embracing energy efficiency and waste reduction. Extra stature go to chemists who carry out desired reactions in the simplest and most elegant ways.

This year chemists showed that they are gaining a new level of control over the molecules they make and how they make them.

When chemists convert a starting compound into one they really want, they typically aim to modify just one of those appendages but not the others.

One group in Israel used a ruthenium-based catalyst to convert starting compounds called amines and alcohols directly into another class of widely useful compounds called amides. A related approach enabled researchers in Canada to link pairs of ring-shaped compounds together. Another minimized the use of protecting groups to make large drug-like organic compounds. Yet another did much the same in mimicking the way microbes synthesize large ladder-shaped toxins. And those are just a few examples. For chemists, it was an efficient year.

Remembering the past, they propose, helps us picture — and prepare for —the future. The notion got a boost this year from several studies hinting at common neural mechanisms for memory and imagination.

In January, researchers in the United Kingdom reported that five people with amnesia caused by damage to the hippocampus, a crucial memory center in the brain, were less adept than healthy volunteers at envisioning hypothetical situations. In April, a brain-imaging study with healthy young volunteers found that recalling past life experiences and imagining future experiences activated a similar network of brain regions, including the hippocampus. Even studies with rats suggested that the hippocampus may have a role in envisioning the future.

On the basis of such findings, some researchers propose that the brain’s memory systems may splice together remembered fragments of past events to construct possible futures. The idea is far from proven, but if future experiments bear it out, memory may indeed turn out to be the mother of imagination.

Computer scientists finally took some of the fun out of the game of checkers. After 18 years of trying, a Canadian team proved that if neither player makes a mistake, a game of checkers will inevitably end in a draw.

The proof makes checkers — also known as draughts — the most complicated game ever ‘solved.’ It marks another victory for machines over humans.

Proving that flawless checkers will end in a stalemate was hardly child’s play. The game is played on an eight-by-eight grid of red and black squares. All told, there are about 500 billion billion arrangements of the pieces, enough to overwhelm even today’s best computers.

So the researchers compiled a database of the mere 39,000 billion arrangements of 10 or fewer pieces and determined which ones led to a win for red, a win for black, or a draw. They then considered a specific opening move and used a search algorithm to show that players with perfect foresight would invariably guide the game to a configuration that yields a draw.

Reported in July, the advance exemplifies an emerging trend in artificial intelligence.

ELIZABETH PENNISI

AND NEWS STAFF

SCIENCE JOURNAL

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