单选题sanger的双脱氧末端终止法DNA序列测定中不需要下列哪种物质?( )

单选题下列各现象中的哪一种不属于自然选择起作用的例子?

单选题由于真菌传染而使某森林所有树的颜色都变成灰白色。多年以后，不同颜色的蛾类增长率最可能的结果是()。

单选题入噬菌体的裂解途径是由以下哪个蛋白基因控制?( )。

单选题烟草属中已发现15个自交不孕的复等位基因S1，S2，S3，…，控制白花授粉的不结实性。这些复等位基因产生的原因是由于______。 A．突变的重演性 B．突变的可逆行 C．突变的多方向性 D．突变的部位不同

单选题转座的结果是导致______。

单选题λ噬菌体的裂解途径是由以下哪个蛋白基因控制?______

单选题Ever since they were first staged in 19th century Europe, world's fairs have enabled people from around the globe to visit wondrous pavilions where they can discover distant lands and new technologies. The 2006 world's fair is no exception, but it also has a decidedly new- era twist: the whole event happens in cyberspace. A nonprofit project dreamed up by Americans Carl Malamud, a computer consultant, and Vinton Cerf, and Internet pioneer and telecommunications-company vice president, the Internet 2006 World Exposition is a digital work in progress, a multi-chambered forum that cybernauts can help build and renovate throughout the year--and perhaps long after the fair's official close in December. While high-tech pavilions set up by sponsoring corporations are featured prominently, as in real fairs, this virtual exposition is closer in spirit and reality to a vast bustling bazaar, a marketplace for the talents and offerings of thousands of individuals and small groups. Anyone with a computer and a modem can not only "attend" but also participate as an exhibitor by creating an individual multimedia Website. Getting the fair up and running was by no means easy. Malamud, 36, spent the past year shuttling among 30 countries, lobbying companies that initially dismissed the project as unwieldy and unworkable. While some nations immediately supported the idea, others completely missed the point of Malamud's vision: to make the fair a public-works project that focuses on what the Internet can offer expert or novice. Once grass-roots groups started backing the project, though, businesses were not far behind. By donating equipment and services, these companies will gain access to millions of potential consumers eager to see the firms' latest technologies. Since the exposition's Jan. 1 launch, as many as 40,000 visitors each day from more than 40 countries have tried the major Websites. Most virtual visitors log on from the U. S and Japan, but the United Arab Emirates, Sweden, Singapore and Estonia have been represented. Comments logged in the fair's guest book are overwhelmingly positive. "Wow, the world is shrinking," wrote a visitor from the Netherlands. Since their initial hesitancy, the major sponsors-primarily telecommunications and software companies--have become firm believers. Beyond the diversity of content and international scope, the fair is a technological marvel. The fastest international link ever installed, this pipeline could be the first step toward laying a permanent network that will eventually hardwire every nation in the world into the Internet. The organizers hope that the infrastructure--and awareness-nurtured by this exposition will launch a boom in Net use.

单选题家猫中有一位于常染色体上的基因杂合时，呈无尾性状；而在纯合体时，又造成致死结果。当一只无尾猫跟另一只无尾猫杂交时，子代表现型为：______。 A．全部无尾 B．无尾:有尾=3:1 C．无尾:有尾=2:1 D．无尾:有尾=1:2

单选题某染色体各区段的线性顺序是abc.defg，变成了abc.dfeg，这叫______。 A．臂内倒位 B．臂间倒位 C．顺接重复 D．反接重复

单选题减数分裂过程中，实现染色体数目减半是在( )分裂的( )。

单选题无籽西瓜是一个同源三倍体，3n=33。在减数分裂时就可能出现______等不同的联会方式，造成后期工不均衡分离，形成的配子基本上都是不育的。 A．三价体和四价体 B．三价体、二价体和单价体 C．二价体和单价体 D．三价体和单价体

单选题以n题为条件，如果小鼠体重的遗传方差为2.7，那么环境方差约为( )。

单选题锥实螺Dd×Dd，后代为( )。

单选题最早用果蝇为材料发现性连锁遗传的科学家是 ____ ，发现果蝇的X染色体不分离现象并直接证明遗传的染色体学说的科学家是 ____ 。

单选题“生存斗争”是什么的结果?( )

单选题可以通过以下______估算环境变量。 A．F1群体 B．BC1群体 C．BC2群体 D．F2群体

单选题在Hfr×F - 杂交中，染色体转移的起点决定于______。

单选题SRY基因：______。 A．是一种果蝇分节基因，决定体节分化 B．是人类Y染色体短臂上的具有男性性别决定作用的基因 C．是X染色体失活中心的调节基因 D．是哺乳动物性连锁基因剂量补偿效应的开关基因