Sunday, December 5, 2010

Life Lines 62


I had the good fortune to attend the CSHL Symposium entitled Evolution: The Molecular Landscape (May 27-June 2, 2009). These annual symposia began in the early 1930s and have made the facility and its programs internationally famous. When I was a graduate student with Muller I took great pleasure going to those meetings. The topics vary but most are on genetics, evolution, neurobiology, and cancer biology. They are informal with lots of opportunities for scientists to have coffee, discuss their work over beer, and stroll along the gorgeous North shore surroundings on this beautiful campus. Muller first introduced me to Jim Watson there (about 1957); and my wife Nedra and I enjoyed our honeymoon there in 1959.

The conference looked at all aspects of evolution from the perspective of molecular biology. Darwin’s evidence for evolution in 1859 was based mainly on domestic breeding, island biogeography with its unusual speciation (as in the Galapagos islands), comparative anatomy, and vestigial organs. There weren’t many fossils available then and dinosaurs were unknown until much later that century. Things changed in the early 1900s with the introduction of Mendelian genetics into population genetics and the genetic basis of variable traits. Chromosome analysis soon revealed an evolution of chromosome number and shape among related species. By the 1950s evolution became biochemical with the working out of biochemical pathways and applying them to gene function and a comparative biochemistry across plants, animals, and microbes. Since the beginning of the 21st century an explosion of papers have appeared using comparative genomics to construct evolutionary phylogenetic trees that correspond to and augment those based on older methods. The major trends revealed by this conference are the newer ways evolution works. The isolation of genes that effect body plans (left-right, head-tail, back-belly, or segmentation) has been introduced into the evolution of phyla. Some simple life forms, such as viruses, can be synthesized from off the shelf chemicals. The evolution of major molecular machines like ribosomes that are involved in protein synthesis have been worked out from bacteria to more recently evolved forms like mammals and flowering plants. Simple molecules of RNA can be followed and selected in test tubes to “evolve” into more complex forms whose functions alter in response to the selection, such as attaching to theophylline (found in teas) instead of caffeine (found in coffee). The evolution of the mammalian clotting mechanism has been worked out, as has the evolution of the receptors for steroid hormones. Craig Venter described his growing collection of 20 million genes he has isolated from the seas and how he can replace the entire genome of a bacterium with a synthetic genome of another species and get it to function and reproduce like that of the donor source.

The most striking thing I learned is that there are relatively few genes needed to account for the domestication of plants (teosinte into maize) or animals (wolves into dogs) and that with the isolation of a dozen or so genes one can create teosinte from maize, or reconstruct 95 percent of the known breeds of dogs from about one dozen genes. It is a dazzling emerging story with lots more to come.

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