摘要脊椎类动物是当前生物物种的重要组成部分之一，它们分布范围广，生活习惯差异较大，而通过查找序列、构建系统发育树我们可以揭示脊椎类动物Tas1rs基因家族的进化规律。此次研究的主要目的是以TAS1R3基因为分子标记重建发育树，系统进化树显示的结果可以直观地显示出这些动物在觉上和在TAS1R3基因上的亲缘关系。构建系统发育树主要依靠比对、搜集DNA序列、蛋白质序列的方式,这两种方法比较常见，除此之外，也有用比较蛋白质的结构的方法来建立生物系统发育树的例子，比较蛋白质的方式主要有刚体结构叠合和多结构特征比较等几种。前述是进行此研究的大体流程，而进行该研究的具体步骤是：（1）在核苷酸数据库（例如NCBI或欧洲分子生物学试验室(ENA)）上查找牛的Tas1r3序列，上述两种数据库是比较权威的，因而查找的相关序列也会相对的比较完整和正确；（2）根据与牛的Tas1r3基因同源性的高低来查找其他脊椎类动物的mRNA序列；（3）将所有的mRNA序列翻译成蛋白质序列（由于密码子的简并性，比对蛋白质序列准确性更高）；（4）使用MEGA，clustalx构建生物系统发育树；（5）分析系统发育树。此次研究通过构建生物系统发育树和系统学分类来了解所有生物的进化历史过程并且研究和探索脊椎类动物的基因同源性，从而得到相关结论，即根据系统发育树所表现出的亲缘性的远近可以预测羊、丛猴、负鼠和大象的Tas1r3基因有失活的可能性。50716

该论文有图2幅，表2个，参考文献10篇。

毕业论文关键词：序列  系统发育树  Tas1r3基因

Tas1r3 gene deactivation tendency in vertebrate animals and the possible causes

Abstract The vertebrate is one of the most important part of the now alive biological species they cover in wide range and have large difference in living habits.However, searching the sequence and construct phylogenetic tree can reveal evolution rule of vertebrate animals Tas1r3 gene families. The main purpose of this study is we use tas1r3 gene as molecular markers to rebuild phylogenetic tree ,the results of phylogenetic tree can show taste sense and the level of homology of Tas1r3 gene of thses animals. Establishing a phylogenetic tree mainly depend on comparing and searching DNA sequences or protein sequences , apart from these two common methods, comparing protein structures also can establish a phylogenetic tree .There are many kinds of methods to compare protein structures , such as rigid body structure, multi structure and so on. The above is the general process of this study ,specific steps of the study are : 1 Find cows Tas1r3 sequence in the nucleotide database(Such as NCBI and the European molecular biology laboratory (ENA)), these databases are authoritative, so we can find more complete and more correct sequence ; 2 According to the level of homology of cattle to find other mRNA sequence of  vertebrate animal; 3 Translate these mRNA sequence into protein sequences (Due to the degeneracy nature of codon, the accuracy of comparing protein sequences is higher). 4 Use the MEGA and clustalx to construct phylogenetic tree; 5 Analyze the Phylogenetic tree. Through the construction of the Phylogenetic tree and systematic taxonomy, we can understand the evolution history process of all vertebrate animal and explore the gene homology of vertebrate animals  , so as to get the concerning conclusion . In other words, according to the genetic distance which is shown in the phylogenetic tree，we can predict the Tas1r3 gene of Sheep、 bush babies、possums and elephants are likely to be inactive. 

Key words:  Sequences  Phylogenetic tree  Tas1r3 gene 

目录

摘要 I

Abstract II