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在黑腹果蝇中，基因ec(棘眼), ct（截翅）, cv（横脉缺失）都是X连锁遗传的。对这三个基因是杂合的ec ct +/++cv的雌蝇与三隐性雄蝇(ec ct cv/Y)交配，统计得到的雄蝇表型结果如下：（10分）测交的子代表型数目ec ct +2125+ + cv2207ec + cv273+ ct +265ec + +217+ ct cv223

这三个基因在染色体上的顺序如何？

答案

参考答案：基因顺序为：Ec、cv、ct（2分）

单项选择题

牙菌斑形成的基础是（）.

A.获得性膜的形成

B.细菌的传递

C.细菌在牙面的初期附着

D.细菌黏附于牙面

E.细菌在牙面共聚
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单项选择题

One of the difficulties in building an SQL-like query language for the Web is the absence of a database (131) for this huge, heterogeneous repository of information. However, if we are interested in HTML documents only, we can construct a virtual schema from the implicit structure of these files. Thus, at the highest level of (132) , every such document is identified by its Uniform Resource Locator (URL), and a (133) and a text. Also, Web severs provide some additional information such as the type, length, and the last modification date of a document. So for data mining purposes, we can consider the set of all HTML documents as a relation:
Document (url, rifle, text, type, length, modif)
Where all the (134) are character strings. In this framework, an individual document is identified with a (135) in this relation. Of course, if some optional information is missing from the HTML document, the associate fields will be left blank, but this is not uncommon in any database.

A．table

B．title

C．driver

D．event
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