And the winner is… human genetic variation. From the journal’s article explaining its choice:

The unveiling of the human genome almost 7 years ago cast the first faint light on our complete genetic makeup. Since then, each new genome sequenced and each new individual studied has illuminated our genomic landscape in ever more detail. In 2007, researchers came to appreciate the extent to which our genomes differ from person to person and the implications of this variation for deciphering the genetics of complex diseases and personal traits.

Less than a year ago, the big news was triangulating variation between us and our primate cousins to get a better handle on genetic changes along the evolutionary tree that led to humans. Now, we have moved from asking what in our DNA makes us human to striving to know what in my DNA makes me me.

Techniques that scan for hundreds of thousands of genetic differences at once are linking particular variations to particular traits and diseases in ways not possible before. Efforts to catalog and assess the effects of insertions and deletions in our DNA are showing that these changes are more common than expected and play important roles in how our genomes work–or don’t work. By looking at variations in genes for hair and skin color and in the “speech” gene, we have also gained a better sense of how we are similar to and different from Neandertals.

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 discover what contributes to red hair, freckles, pudginess, or a love of chocolate–let alone quantifying 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.

And what about cell reprogramming? If you had money on it to show, you win. It was #2 on the Science list. Donald Kennedy, the journal’s editor-in-chief, addresses that development in an accompanying commentary:

A strong Breakthrough runner-up arrived at this year’s finish line just in time. Two new studies, one published in Science, showed how adult human epithelial cells could be reprogrammed, through the virally mediated introduction of just four genes, to behave like pluripotent cells; that is, able to act as embryonic stem cells do, to produce every descendent cell type. This breakthrough has produced some relief, but it also comes with some reservations. James Thompson of the University of Wisconsin, who did the first research with embryonic stem cells, has now taken a major step toward ending the “ethical” controversy over their use. But hold on: That controversy was generated by specific objections from one religion, not some universal ethic. There is every reason to continue research along the old path, with embryo-derived cells: The new methods may carry unknown liabilities, so making the case for changing Bush’s 2001 presidential order should continue.

The whole list is posted at Science’s site.

-Greg Dahlmann