In this dissertation, we systematically studied the evolutionary patterns of yeasts, elapid snakes and sheep at the genomic and transcriptomic level. The budding yeast（Saccharomyces cerevisiae）is the first completely sequenced eukaryote and the genomic sequences of its relative species or strains were also available available during the last decade. We identified about 40 introgression segments between S. cerevisiae and its sibling species S. paradoxus, by screening the nuclear-sequence data from 73 globally distributed natural and domesticated yeast populations. As new useful genetic markers, the gene flow events indicate S. cerevisiae was originated from Europe and expend to other continents after S. paradoxus had been a global microbe. We identified dozens of new duplicated genes and two de novo originated genes in S. cerevisiae. Kraits and cobras are two representative toxic genera of elapids in the old world. To unveil their detailed venoms and their evolutionary patterns, we constructed venom gland cDNA libraries and genomic bacterial artificial chromosome（BAC） libraries for Bungarus multicinctus and Naja atra, respectively. We sequenced the venom transcriptomes and screened the BAC libraries of the two snakes by blot analysis. Based on the toxin ESTs and the three finger toxin（3FTx）gene sequences, the major components of the two venom transcriptomes were well known. The data also revealed that tandem duplications contributed the most to the expansion of toxin multigene families. Thanks to the use of next-generation sequencing tools, the big genome of domesticated animals become more easily available. We finished the sequencing, de novo assembly and annotation of the draft reference sheep（Ovis aries）genome. The N50 length of the assembled scaffolds is 1.1Mb, and the scaffold sets achieve a total length of 2.71 Gb, which covers approximately 91% of the whole sheep genome. Using both the male and female Texel sequence, we separately identified about 5 million heterozygous single nucleotide polymorphisms. Seven tissue samples derived from the same Texel ewe were used for Illumina mRNA-seq to define the expressed portion of the genome. Through comparative genomic analysis, we have built the ruminant orthology database, and analysed the adaptability in mountainous areas and the economic characters for sheep.
修改评论