填空题Long before man lived on the Earth, there were fishes, reptiles, birds, insects, and some mammals. Although some of these animals were ancestors of kinds living today, others are now extinct, that is, they have no descendants alive now. Nevertheless, we know a great deal about many of them because their bones and shells have been preserved in the rocks as fossils. 41.______That kind of rock in which the remains are found tells us much about the nature of the original land, often of the plants that grew on it, and even of its climate. When an animal dies, the body, its bones, or shell, may often be carried away by streams into lakes or the sea and there get covered up by mud. If the animal lived in the sea its body would probably sink and be covered with mud. More and more mud would fall upon it until the bones or shell become embedded and preserved. 42．______Thus it follows that there must be many kinds of mammals, birds, and insects of which we know nothing, 43．______Later forms are more complex, and among these are the sea-lilies, relations of the star-fishes, which had long arms and were attached by a long stalk to the sea bed, or to rocks. There were also crab-like creatures, whose bodies were covered with a horny substance, The body segments each had two pairs of legs, one pair for walking on the sandy bottom, the other for swimming. The head was a kind of shield with a pair of compound eyes, often with thousands of lenses. They were usually an inch or two long but some were 2 feet. The shellfish have a long history in the rock and many different kinds are known. Of these, the ammonites are very interesting and important. They have a shell composed of many chambers, each representing a temporary home of the animal. As the young grew larger it grew a new chamber and sealed off the previous one. Thousands of these can be seen in the rocks on the Dorset Coast. The first animals with true backbones were fishes, first known in the rocks of 375 million years ago. About 300 million years ago the amphibians, the animals able to live both on land and in water, appeared. They were giant, sometimes 8 feet long, and many of them lived in the swampy pools in which our coal seam, or layer, formed. 44．______About 75 million years ago the Age of Reptiles was over and most of the groups died out. The mammals quickly developed, and we can trace the evolution of many familiar animals such as the elephant and horse. 45．______ [A] The best index fossils tend to be marine creatures. These animals evolved rapidly and spread over large areas of the world. [B] The amphibians gave rise to the reptiles and for nearly 150 million years these were the principal forms of life on land, in the sea, and in the air. [C] Many of the later mammals, though now extinct, were known to primitive man and were featured by him in cave paintings and on bone carvings. [D] Nearly all of the fossils that we know were preserved in rocks formed by water action, and most of these are of animals that lived in or near water. [E] The earliest animals whose remains have been found were all very simple kinds and lived in the sea. [F] Many factors can influence how fossils are preserved in rocks. Remains of an organism may be replaced by minerals, dissolved by an acidic solution to leave only their impression, or simply reduced to a more stable form. [G] From them we can tell their size and shape, how they walked, the kind of food they ate. Very occasionally the rocks show impression of skin, so that, apart from color, we can build up a reasonably accurate picture of an animal that died millions of years ago.

填空题DNA结合结构域的常见结构有______、______、______、______和______。

填空题 翻译延长阶段的进位，是指( )进入( )位。翻译延长阶段的转位是指( )与( )做相对运动。

填空题当溶液中盐离子强度低时，可增加蛋白质的溶解度，这种现象称为______；当溶液中盐离子强度高时，可使蛋白质沉淀，这种现象称为______。

填空题将1/%的重组或重组频率作为度量单位，叫厘摩(centimorgan，cM)或______。

填空题不同细菌出现感受态的时期是不同的，如肺炎球菌感受态出现的时期是______，而枯草杆菌感受态的出现是在______。

填空题利福霉素类药抑制RNA合成的______，链霉溶菌素抑制RNA链的______。肝素是一种酸性黏多糖，与核酸竞争______而妨碍了与有意义链的结合。

填空题酵母交配型相关的三个开关基因座分别是______、______和______。

填空题λ噬菌体载体由于受到包装的限制，插入外源DNA片段后，总的长度应在噬菌体基因组的______的范围内。

填空题结构基因组学是通过______的实施来完成的。以全基因组测序为目标的基因结构研究，弄清基因组中全部基因的位置和结构，为基因功能的研究奠定基础。其目的是建立高分辨的______、______、______和______。

填空题基因芯片主要分为______、______和______。

填空题如果DNA聚合酶出现错误，会产生一对错配碱基，这种错误可以被一个通过甲基化作用来区别新链和旧链的差别的______系统进行校正。

填空题DNA的物理图谱是DNA分子的______片段的排列顺序。

填空题在球状蛋白质分子中，______氨基酸残基的侧链分布于分子表面，而氨基酸残基的侧链位于分子内部。

填空题研究蛋白质与蛋白质相互作用的技术有______、______和______。

填空题 大肠杆菌的变异株在没有乳糖存在时大量产生-半乳糖苷酶。这种变异株的产生是由于( )的突变，因而不能生成( )，或者由于( )突变，( )不能和( )结合，所以没有乳糖( )也可活动。

填空题 基因的分子生物学定义是( )。

填空题体内两种主要的环核苷酸是______和______。

填空题绘制遗传学图时，基因定位所采用的主要方法有两种，即______和______。

填空题将含有一个mRNA的DNA拷贝的克隆称作一个______，源于同一批RNA制备物的克隆群则构建了一个______。