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Making Life from Scratch

Artificial intelligence is not human intelligence, nor is synthetic life the same as life with evolutionary history.

Robert L. Dorit

Reassembling Life

A second approach in synthetic biology, the top-down strategy, aims to create customized organisms from a growing catalog of existing molecular parts. Proponents of this second approach argue that biologists have finally come to describe and understand living systems in sufficient detail that they can now customize those systems to create specific desired outcomes and address specific human needs. I call this the “LEGO view” of the world. Here, the genome is regarded simply as the sum of its parts. These parts are, in effect, modular, and supposedly retain their integrity and function independent of the context in which they occur. If this were so, biological engineers would be able to select desired genes, assemble them into a genome and, in so doing, give rise to an organism that might never have evolved on its own.

Modularity, particularly at the molecular level, seems at first to be quite common in the living world and underlies the entire biotechnology revolution. Modularity, after all, enabled early practitioners to transfer a human gene into the genome of a bacterium and still have it direct the the production of a desired human protein. Nature, too, often trades in modular subunits: Protein domains, individual genes, or clusters of genes that confer particular phenotypes (for example, resistance to multiple antibiotics) have moved from one location within a genome to another, or from one genome to another, all the while retaining their integrity and function. For example, the well-known Hox genes, responsible for controlling embryonic development along a central axis, have undergo

ne repeated expansions, contractions, duplications, and changes of address within eukaryotic genomes while retaining their fundamental role: determining crucial patterns of early development in multicellular animals. And even larger genome segments spanning thousands of genes have, over evolutionary time, moved from one location to another without losing their function.

A short leap separates these observations from the conviction that all genetic information is fundamentally modular, and so can be disassembled and reassembled in virtually infinite combinations. As the catalog of known genetic elements continues to grow, the vision of creating organisms that will do exactly what researchers want them to do beguiles. Synthetic biology promises that the power of the living world, fully dissected and deconstructed in the first triumphant half-century of the Age of Biology, will finally be brought to bear in solving humanity’s most complex and recalcitrant problems, from the production of virtually inexhaustible food supplies to the waste-free transformation of sunlight into usable energy.

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