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Scientists have borrowed a simple word from everyday speech—transcription—to encompass the steps required to generate the instructions to activate specific genes. Except that the biochemical process of “transcribing” a gene is so ornate that it's rather like having to whittle the pencil, make the paper, and assemble the components for a desk and chair before you can sit down to begin copying your roommate's lecture notes—each and every time.
This isn't a manufacturing process that an engineer would devise, if given the opportunity. Rather, this almost Rube Goldberg-like assembly could take hold only through a random trial-and-error process such as evolution. And that is one reason I have found transcription so fascinating for better than 30 years. What events initiate the process? How do the essential molecules assemble? Does the machinery vary? What cues enable RNA polymerase—the enzyme that makes messenger RNA—to latch onto the right snippet of DNA and begin assembling a transcript?
Nothing we study in biology and medicine would have a rational, predictable foundation without Charles Darwin's insights into evolution, the process of ceaseless experimentation that drives an organism's ability to adapt and survive over huge spans of time. Throughout this issue of the HHMI Bulletin, we consider different aspects of evolution: from how teachers introduce basic concepts to their students to the mathematical models used by HHMI investigator Jonathan Pritchard to gauge the impact of natural selection on human traits. We conclude with Darwin's magisterial prose, honoring the 150th anniversary of the publication of The Origin of Species.
Many Americans struggle with the fundamentals of evolution and whether to accept its tenets. As teacher Suzanne Black has discovered, focusing on relevant concrete examples is often the best approach. After all, without a firm understanding of evolution, scientists would have been utterly stumped by the new strain of influenza that is sweeping the world. The H1N1 strain of influenza is a mixed pot of genes drawn from viruses that infect pigs in Eurasia and the Americas, birds, and humans. By looking at changes in the proteins that dot the surface of the virus—changes that help the virus survive and adapt—researchers can assess its evolutionary path and map a vaccine strategy for the upcoming flu season. Likewise, each time a forensic scientist uses a sample of DNA from a crime scene to screen potential suspects, knowledge of evolution comes into play because each person's genetic signature is unique yet related and predictable in its relationship to other individuals. Such everyday examples have been compiled by colleagues at the National Academy of Sciences in the book Science, Evolution and Creationism, a survey of modern evolutionary biology written for the public. A free PDF is available at www.nap.edu/sec.
Photo: Barbara Ries
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