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【简答题】
Summer Job The summer job is a tradition among students in American colleges. Long before the end of the school year, students begin their search for a job during the summer vacation. They send letters to businesses, talk to employers about job opportunities during the summer, and ask friends to help them get a job. Typist, salesclerk, lifeguard and waiter are some of the common jobs that students often do during the summer months. But many young people find work that is a little more unusual than some of the jobs just mentioned. Climbing ranger Bob works as a climbing ranger among the beautiful mountains in the American West. He has two important tasks. Three days a week he is in charge of a ranger station. In this job he checks all the people--- nearly 3,000 every summer--- who want to climb the mountains. For the rest of the week, he and his five-man team walk around the mountains to see if anything unusual is happening. At the same time, they give directions to people who are climbing the mountains, check their climbing conditions, and make rescues when necessary. Park guide Dody has spent the past three summers in Yellowstone National Park. Her job is to help the thousands of tourists who visit Mammoth Hot Springs to know better about the many springs and the unusual terraces formed by their deposits. She leads nature walks through the terraces, presents a slide show, gives talks around campfires, and answer questions at the visitor's center. Ranch hand Last summer, Steve got a chance to get away from the city. He worked on a big sheep ranch in western Wyoming. The ranch covers miles of desert, grassland and mountains. Steve's work began when the sun rose and continued until 6:30 in the evening--- seven days a week. He spent most of his time making hay. He said, " It's good for me to have a taste of a kind of work that I'd never known before."
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【单选题】下列关于各种类型操纵子的叙述,正确的是
A.
乳糖操纵子在无乳糖时开放
B.
阿拉伯糖操纵子中CAP起正调控作用
C.
色氨酸操纵子在有色氨酸时开放
D.
乳糖操纵子的阻遏物是一种变性蛋白
E.
阻遏物是否结合于操纵区,可以决定操纵子的关闭或开放
【单选题】下列关于各种类型操纵子的叙述,正确的是
A.
乳糖操纵子在无乳糖时开放
B.
阿拉伯糖操纵子是可阻遏型操纵子
C.
色氨酸操纵子在有色氨酸时开放
D.
乳糖操纵子的阻遏物是一种变性蛋白
E.
阻遏物是否结合于操纵区,可以决定操纵子的关闭或开放
【简答题】X射线透过物质时产生的物理效应有( )、( )、( )和( )。
【多选题】X射线通过物质时产生的物理效应有: 、 、 、和 。
A.
散射
B.
光电效应
C.
透射X射线
D.
【单选题】下列关于色氨酸操纵子调控的叙述,正确的是 ( )
A.
色氨酸存在时,仅生成前导mRNA
B.
无色氨酸时,转录抑制
C.
是翻译水平的调控
D.
具有抗终止的作用
E.
色氨酸存在时,去阻遏
【判断题】"一国两制"的前提是大陆实行社会主义制度。
A.
正确
B.
错误
【简答题】“”实行的大前提是( )
【单选题】通过学习通教学平台,能够增强自主学习能力?
A.
非常符合
B.
符合
C.
不符合
D.
非常不符合
【判断题】一国两制 ”的前提是大陆实行社会主义制度
A.
正确
B.
错误
【多选题】色氨酸是人和动物的必需氨基酸,下图为原核生物细胞内色氨酸的合成机制示意图。下列有关叙述正确的是 ( )
A.
基因 “ 开启 ” 和 “ 关闭 ” 的调节机制属于反馈调节
B.
阻遏蛋白和色氨酸结合后阻止 RNA 聚合酶结合 RNA
C.
色氨酸操纵子的转录和翻译在时间和空间上是先后、分开进行的
D.
人体内不存在相应的色氨酸操纵子和色氨酸合成机制
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