 James Urton |
James R. UrtonGraduate Research Associatejurton@u.washington.edu
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Research InterestsI am currently a student in the Molecular and Cellular Biology Graduate Program at the University of Washington. I joined the Peichel lab in 2006 to further my interests in molecular biology and evolution.The six species within the stickleback family (Gasterosteidae) represent an irresistible opportunity to investigate genome evolution and genetic sex determination pathways. Many model sex chromosome systems are relatively ancient (the mammalian Y, for example, is over 300 million years old); thus, much of what we know about the "early" steps in vertebrate sex chromosome evolution must be inferred through the numerous rearrangements, deletions, and translocations found on highly degenerate sex chromosomes. In the stickleback fishes, however, which last shared a common ancestor as little as twenty million years ago, genetic and cytogenetic evidence indicates that at least two sex chromosome systems have evolved. The XY sex chromosomes of the threespine, black-spotted, and ninespine sticklebacks are likely derived from a common ancestor and are unrelated to the ZW sex chromosome system of the fourspine stickleback. How did these two systems evolve? Was one present in the common stickleback ancestor? Do the two remaining members of the stickleback family (the brook and fifteenspine sticklebacks) have genetic systems of sex determination? If so, are they related to the XY or ZW systems? What master sex determination gene(s) are present in the XY and ZW sex chromosome systems? Are they related to sex determination genes known from other vertebrates? I hope to address these and other questions regarding stickleback sex determination pathways. | ||
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I would also like to compare the threespine stickleback X and Y chromosome sequences for evidence of dosage compensation. The evolution of sex chromosomes (XY or ZW) creates a hemizygous state in one sex, as the Y and W chromosomes often accumulate mutations and transposable elements and subsequently physically degenerate compared to their X and Z counterparts. The female (XX) threespine stickleback genome has been sequenced, and, upon completion of the Y chromosome sequence, I will systematically examine the levels of sequence divergence and degeneration of Y-linked alleles; I will also compare expression levels from X and Y-linked alleles to determine if there is evidence of dosage compensation. This could establish the threespine stickleback as a model system for studying the early stages in the evolution of dosage compensation.
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Page Last Updated: 6 December 2007
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