Evolution of heteromorphic sex chromosomes in Reptilia

描述(申请人提供)：最近创建的细菌人工染色体(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。性别决定(SD)基因在一些物种的性染色体上被发现，在其他物种的常染色体上也被发现。在性染色体或常染色体上一致发现的SD基因的鉴定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没有发现Sry同源物。我们将使用荧光原位杂交和染色体涂色来定位具有代表性的爬行动物和鸟类中的SD基因。我们将比较SD基因的序列。我们对SD基因和合成体的定位将与异性配子模式和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以下问题：鸟类和爬行动物性别分化的启动，具有遗传或环境SD机制的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染色体异形的历史。

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.