中间图

Or

雷哥网GMAT>题库>精选题库>阅读RC>9664

阅读RC-9664 (第12/12题) Time Cost00:00
收藏
报告题目错误
请选择错误类型:
请描述一下这个错误:

取消

All the cells in a particular plant start out with the same complement of genes. How then can these cells differentiate and form structures as different as roots, stems, leaves, and fruits? The answer is that only a small subset of the genes in a particular kind of cell are expressed, or turned on, at a given time. This is accomplished by a complex system of chemical messengers that in plants include hormones and other regulatory molecules. Five major hormones have been identified: auxin, abscisic acid, cytokinin, ethylene, and gibberellin. Studies of plants have now identified a new class of regulatory molecules called oligosaccharins.

Unlike the oligosaccharins, the five well-known plant hormones are pleiotropic rather than specific ; that is, each has more than one effect on the growth and development of plants. The five have so many simultaneous effects that they are not very useful in artificially controlling the growth of crops. Auxin, for instance, stimulates the rate of cell elongation, causes shoots to grow up and roots to grow down, and inhibits the growth of lateral shoots. Auxin also causes the plant to develop a vascular system, to form lateral roots, and to produce ethylene.

The pleiotropy of the five well-studied plant hormones is somewhat analogous to that of certain hormones in animals. For example, hormones from the hypothalamus in the brain stimulate the anterior lobe of the pituitary gland to synthesize and release many different hormones, one of which stimulates the release of hormones from the adrenal cortex. These hormones have specific effects on target organs all over the body. One hormone stimulates the thyroid gland, for example, another the ovarian follicle cells, and so forth. In other words, there is a hierarchy of hormones.

Such a hierarchy may also exist in plants. Oligosaccharins are fragments of the cell wall released by enzymes: different enzymes release different oligosaccharins. There are indications that pleiotropic plant hormones may actually function by activating the enzymes that release these other, more specific chemical messengers from the cell wall.

The passage suggests that, unlike the pleiotropic hormones, oligosaccharins could be used effectively to

  • 分析A选项
    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
  • 分析B选项
    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
  • 分析C选项
    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
  • 分析D选项
    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
  • 分析E选项
    xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
暂无雷哥网文字解析
当前版本由 kisenana 更新于2015-11-05 15:55:06 感谢由 kisenana 对此题目的解答所做出的贡献。
推理题,问的是O的作用,且题目中有O和5H的对比,那么找有他们对比的地方
定位到第二段
这里说的是不同于O,5H的特点:多效性,因为多效性,通过5H人工控制庄稼生长不太有用。
那么题目问的是O,反过来说,O是专一的,可以有效控制庄稼生长
选项A trace the passage of chemicals through the walls of cells未提及
选项B O可以被有效地用于 pinpoint 其他植物荷尔蒙得功能,文章未提及
选项C 正确
选择D O可以被有效地用于 alter the complement of genes 文章未提及,直说了O和5H可以控制基因表达,没有说可以改变机经组成
选项E 改变5H 的effect 未提及

题目讨论 (3条评论)

用户头像
提交
  • 用户头像
    329247atnr

    原文没有提到的内容竟然可以这样意淫吗?????five hormones不能用与控制,oligo就可以吗?不一定吧
    1 0 回复 2022-10-29 23:33:41
  • 用户头像
    700一定行

    妈的我是瞎子
    0 0 回复 2022-08-03 10:53:18
  • 用户头像
    Balala

    Unlike the oligosaccharins, 。。。。。。。 The five have so many simultaneous effects that they are not very useful in artificially controlling the growth of crops.
    0 0 回复 2021-01-01 11:16:36
    题号选择

    科目: 阅读RC

    • 句子改错SC
    • 逻辑CR
    • 阅读RC
    • 数据充分DS
    • 问题求解PS
    • 综合推理IR

    来源: 精选题库

    • 全部
    • OG20
    • OG20新题
    • OG19新题
    • OG18新题
    • OG18分册
    • OG17新题
    • OG16
    • OG12
    • 破解版12
    • 破解版08
    • 破解版07
    • GWD
    • 精选题库
    • OG18自测章
    • Manhattan
    • magoosh
    • 难题300
    本题信息

    1m54s

    平均耗时

    67.7%

    平均正确率

    • 题目来源1:精选题库

    该题由网友3FKDNmL提供 上传GMAT题

    • 手机注册
    • 邮箱注册
    登录>







    关闭图标

    标题图

    • 图标

      知识库学习

      GMAT语法、逻辑、阅读、数学各单项备考知识点学习及测验
    • 图标

      在线做题

      包含GMAT各单项必考知识点题目、OG/PREP/GWD/雷哥讲义题目、难度650/680/700/730题库题目练习及题目解析
    • 图标

      在线模考

      语文套题/数学套题/全套仿真模考,包含GWD/PERP/精选模考等上百套套题模考
    • 图标

      在线测评

      适合5种不同基础的GMAT学员,测评后可自动出具分数报告及复习计划指导
    • 图标

      资料下载

      GMAT必备备考资料下载、鸡精下载、课程课件等免费下载
    • 图标

      课程学习

      注册会员后,可在GMAT课程区,选择免费直播课程及公开课程进行在线学习
    ×
    请你选择你要查看的模考成绩单
    立即开通 暂不开通
    加载图片
    网络异常