Evolution of heteromorphic sex chromosomes in Reptilia

描述（由申请人提供）：最近建立的细菌人工染色体（BAC）文库将使我们能够对爬行动物和鸟类的部分性染色体进行测序和比较。在一些物种的性染色体和其他物种的常染色体上发现了性别决定基因。在性染色体或常染色体上发现一致的SD基因，可以解释环境和遗传上SD物种性别分化的开始。例如，Y染色体上的Sry基因启动哺乳动物的性别分化。在非哺乳动物脊椎动物中未发现Sry同源物。我们将利用荧光原位杂交和染色体涂画技术定位具有代表性的爬行动物和鸟类的SD基因。我们将比较SD基因的合成。我们的SD基因定位和合成将与异配子模式和SD机制进行比较。我们广泛的比较基因组学方法将使我们能够解决有关鸟类和爬行动物性别分化的开始，遗传或环境SD机制下物种之间的基因组差异，染色体退化的原因以及鸟类和爬行动物异型染色体的历史等问题。

DESCRIPTION (provided by applicant): The recent creation of bacterial artificial chromosome (BAC) libraries will allow us to sequence and compare portions of sex chromosomes among reptiles and birds. Sex-determining (SD) genes have been found on sex chromosomes in some species and on autosomes in other species. Identification of SD genes consistently found in synteny on either sex chromosomes or autosomes could explain the initiation of sex differentiation in environmentally and genetically SD species. For example, the Sry gene on the Y chromosome initiates sex differentiation in mammals. No Sry homolog has been found in non-mammalian vertebrates. We will use flourescent in situ hybridization and chromosome painting to locate SD genes in representative reptiles and birds. We will compare syntenies of SD genes. Our mapping of SD genes and syntenies will be compared with patterns of heterogamety and SD mechanism. Our broad approach to comparative genomics will allow us to address questions about initiation of sex differentiation in birds and reptiles, genomic differences between species with either genetic or environmental SD mechanisms, causes of chromosomal degeneration, and the history of heteromorphic chromosomes in birds and reptiles.