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191ple grains or crystals with different crystal-lographic orientations that are separated bygrain boundaries. As a result of plastic de-formation, the original grains are subdivid-ed into smaller grains separated by disloca-tion (line defect) networks. Moreover,commercial alloys always contain impuri-ties that can form precipitates, which aresmall particles with a different composi-tion and crystal structure than the matrix. Schmidt et al. have determined the ab-solute crystallographic orientation, posi-tion, volume, and shape of a recrystallizinggrain in deformed aluminum. Their workshows that the shape of a recrystallizinggrain in aluminum is more or less sphericalas it starts to grow, in accordance with gen-eral belief, but as it grows the grain pro-gresses in different directions with differ-ent speeds and in a jerky fashion. The mo-bility of the grain boundary, which is animportant parameter in models, is unam-biguously determined and shown to beanisotropic. The authors show that thejerky movement of the grain boundary re-flects the inhomogeneous distribution ofdislocations in the deformed aluminummatrix. Knowledge about the density, dis-tribution, and arrangement of the disloca-tion in the deformed matrix and their influ-ence on the growth of an individual grain,as measured by Schmidt et al., is of utmostimportance in understanding recrystalliza-tion phenomena.The authors measured the recrystalliza-tion process in exceptional detail, which isof great value for theoreticians becausetheory and experiment can now be com-pared at the elementary level of a singlegrain. Characterizing microstructures in4D opens great opportunities in otherfields of materials science. For example, itshould now be possible to study the under-lying mechanisms of solidification, solid-state phase transformations, and precipita-tion of a wide range of materials. As a re-sult, the 3DXRD technique will contributeto the development of materials with supe-rior properties and optimal productionroutes.References and Notes1. S. Schmidt et al.,Science 305, 229 (2004).2. J. P. Hall, Z. Z. Petch,Can. J. Metallurgy26, 254 (1954).3. D. Larbalestier et al.,Nature414, 368 (2001).4. R. J. Young, P. A. Lovell,Introduction to Polymers(Chapman & Hall, London, ed. 2, 1991).5. M. V. Kral, M. A. Mangan, G. Spanos, R. O. Rosenberg,Mater. Charact. 45, 17 (2000).6. M. Onink et al.,J. Mater. Sci. 30, 6223 (1995).7. Supported by the Dutch Technology Foundation (STW)of the Netherlands Organization for Scientific Research(NWO).These are exciting times for those in-terested in human origins. After al-most a century of knowledge gleanedfrom the excavation of hominid bones inEast Africa, the draft sequence of the chim-panzee genome is now providing a flood ofmolecular data that may shed new light onhuman origins. The challenge of integrat-ing these molecular data with the fossilrecord and with behavioral studies of greatapes was on full display during a recentsymposium at the University of California,San Diego (1). Most speakers discussed one of threeprincipal sources of data: a Japanese-ledanalysis of chimp chromosome 22 (2); aprivate-sector initiative at Celera Genom-ics to sequence most of the exons of thechimp genome (3); and the NationalHuman Genome Research Institute(NHGRI)–funded project to produce arough-draft sequence of the whole chimpgenome (4). Although the recent release ofthe draft sequence by the WashingtonUniversity and MIT/Broad Institute se-quencing centers (4) was the primary im-petus for this symposium, many other as-pects of our closest evolutionary relativealso were explored.Yoshiyuki Sakaki (RIKEN GenomicsSciences Center) represented the Japanese-led effort. Although this project analyzedonly ~1% of the chimpanzee genome, itprovides the first look at long-range com-parisons with the human genome based oncomplete high-quality sequence. The long-range organization of chimpanzee chromo-some 22 is nearly identical to that of its hu-man homolog, chromosome 21. The level ofsingle–base pair substitutions between thetwo species is only 1.44%. However, thereare tens of thousands of insertion-deletionvariants, including one 200-kbp human-spe-cific duplication. Many sequence variationsbetween the chimp and human lineages areattributable to differing activities of largenumbers of retrotransposons.Andy Clark (Cornell University), repre-senting Celera’s exon sequencing effort,discussed chimp-human comparisons ofinferred protein sequences. Interestingly,proteins involved in amino acid catabolismshowed a big positive selection signal inthe human lineage, whereas those involvedin neural development did not. This find-ing reminds us that diet and pathogens aredominant selective forces for all species.Other genes undergoing rapid positive se-lection in the human lineage include thoseencoding proteins that are involved in hear-ing, such as α-tectorin, a structural inner-ear protein. Evan Eichler (Case WesternReserve University), who based his analy-sis on the rough-draft whole-genome se-quence, emphasized the same point. He re-ported major deletions in the chimpanzeegenome, totaling at least 8 Mbp, which in-clude a number of genesassociated with immuni-ty and inflammation.Eichler also discussedthe presence in the chim-panzee of many copiesof a retroviral provirusthat is absent from thehuman genome. Its pres-ence in chimpanzees,bonobos, gorillas, andOld World monkeys—but not humans, orang-utans, and gibbons—suggests multiple, inde-pendent instances ofhorizontal transmission.This serves as anotherGENOMICSThe Chimpanzee Genome—A Bittersweet CelebrationMaynard V. Olson and Ajit VarkiM. V. Olson is at the University of WashingtonGenome Center, Departments of Medicine andGenome Sciences, Seattle, WA 98195, USA. A. Varki isat the Glycobiology Research and Training Center,Departments of Medicine and Cellular and MolecularMedicine, University of California at San Diego, LaJolla, CA 92093, USA. E-mail: [email protected];[email protected] ERSPECTIVESwww.sciencemag.org SCIENCE VOL 305 9 JULY 2004192reminder that a dominant force shaping pri-mate genomes has been the proliferation ofmobile elements of various kinds. Providing an overview of the rough-draft whole-genome sequence, RobertWaterston (University of Washington) dis-cussed evidence for the possible rapid evo-lution of genes involved in host defense, us-ing protease genes as an example.Discussing another aspect of primate inter-actions with the environment, Svante


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UIUC IB 201 - The Chimpanzee Genome

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