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  • RNA 核纳

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    A Deceptively Simple Model
    ::欺骗性简单模型Name

    This simple model sums up one of the most important ideas in biology , which is called the central dogma of molecular biology (you'll read more about it below). You probably recognize the spiral-shaped structure on the left. It represents a molecule of , the biochemical molecule that stores genetic information in most living . The globular structure on the right represents a . Proteins are the class of biochemical molecules that carry out virtually all life processes. What is the structure in the center of the model? It appears to resemble DNA, but it is smaller and simpler. This molecule is the key to the central dogma, and it may have been the first type of biochemical molecule to evolve.
    ::这个简单的模型总结了生物学中最重要的思想之一, 也就是分子生物学的中心教条( 您将在下面阅读更多关于它的内容) 。 您可能认得左侧的螺旋形结构。 它代表着一个分子, 生物化学分子, 它储存着最活的基因信息 。 右边的球状结构代表着一个 。 蛋白质是生物化学分子的类别, 它几乎贯穿了所有生命过程。 模型的中心结构是什么? 它看起来类似于DNA, 但是它更小, 更简单。 这个分子是中央教条的关键, 它可能是第一种进化的生化分子。

    Central Dogma of Molecular Biology
    ::分子生物学中心犬目

    DNA is found in . In eukaryotic cells , chromosomes always remain in the , but proteins are made at in the cytoplasm . How do the instructions in DNA get to the site of outside the nucleus?
    ::DNA在 . 在 eukaryaty 细胞中, 染色体总是留在细胞中, 但蛋白质是在细胞托盘中生成的。 DNA中的指令如何到达核外的场地 ?

    Another type of is responsible. This nucleic acid is RNA , or ribonucleic acid. RNA is a small molecule that can squeeze through pores in the nuclear membrane. It carries the information from DNA in the nucleus to a ribosome in the cytoplasm and then helps assemble the protein. In short:
    ::这种核酸是RNA,或者说肋骨细胞酸。RNA是一种小分子,可以通过核膜的孔隙挤压。它把核核核核核核核核素的DNA信息传送到细胞托盘上的核素,然后帮助组装蛋白质。简而言之:

    DNA → RNA → Protein
    ::DNA RNA 蛋白质

    This expresses in words what the model shows. The genetic instructions encoded in DNA in the nucleus are transcribed to RNA. Then, RNA carries the instructions to a ribosome in the cytoplasm, where they are translated into a protein. Discovering this sequence of events was a major milestone in molecular biology. It's called the central dogma of molecular biology .
    ::以文字表达模型所显示的。 核中以DNA编码的基因指示被转录到 RNA 。 然后, RNA 将指示转录到细胞托盘中的血清, 并转换成蛋白质。 发现这一系列事件是分子生物学中的一个重要里程碑。 它被称为分子生物学的核心教条 。

    Introducing RNA
    ::介绍RNA

    DNA alone cannot “tell” your cells how to make proteins. It needs the help of RNA, the other main player in the central dogma of molecular biology. Like DNA, RNA is a nucleic acid, so it consists of repeating nucleotides bonded together to form a polynucleotide chain. Also like DNA, each RNA nucleotide consists of a sugar, a phosphate group, and a nitrogen base. However, RNA differs from DNA in several ways. Unlike DNA, RNA:
    ::DNA不能单独“ 讲述” 你细胞如何制造蛋白质。 它需要DNA的帮助, RNA是分子生物学中心教条中的另一个主要玩家。 和DNA一样, RNA是一种核酸,因此它包括重复核糖核酸结合以形成一个多核酸链。 和DNA一样, RNA的核酸由糖、磷酸组和氮基组成。 但是, RNA与DNA有不同之处。 与DNA不同, RNA:

    • consists of one polynucleotide chain instead of two
      ::由一个圆核核酸链组成,而不是两个
    • contains a nitrogen base called uracil (U) instead of thymine
      ::含氮基,称为uracil(U),而非甲状腺。
    • contains the sugar ribose instead of deoxyribose
      ::糖含肋骨而不是脱氧核糖

    The following animated figure represents an RNA molecule. Can you identify an individual nucleotide and each of its main components?
    ::以下动画图表示 RNA 分子。 您能否辨别一个单核核素及其每个主要成分 ?

    This rotating RNA model reveals the structure of the molecule.
    ::这种旋转式RNA模型揭示了分子的结构。

    Functions of RNA
    ::RNA RNA 函数

    The main function of RNA is to help make proteins. There are three main types of RNA involved in protein synthesis:
    ::RNA的主要功能是帮助生产蛋白质,蛋白质合成主要有三种RNA类型:

    1. Messenger RNA (mRNA) copies (or transcribes) the genetic instructions from DNA in the nucleus and carries them to the cytoplasm.
      ::送信人RNA(mRNA)复制(或抄录)核中DNA的遗传指示,并携带到细胞托盘上。
    2. Ribosomal RNA (rRNA) helps form ribosomes, where proteins are assembled. Ribosomes also contain proteins.
      ::RRNA(RNA)帮助形成蛋白质组装的骨质。 Riboomomes也含有蛋白质。
    3. Transfer RNA (tRNA) brings amino acids to ribosomes, where rRNA catalyzes the formation of chemical bonds between them to form a protein.
      ::转移RNA(tRNA)将氨基酸引入血清,而RRNA会催化它们之间形成化学联系以形成蛋白质。

    In the concept Protein Synthesis , you can read in detail about how these three types of RNA help cells make proteins.
    ::在蛋白质合成概念中,你可以详细阅读这三种RNA帮助细胞如何产生蛋白质。

    RNA is a very versatile molecule that plays multiple roles in living things. In addition to helping make proteins, for example, there are RNA molecules that regulate the expression of genes , and RNA molecules that catalyze other needed to sustain life. Because of the diversity of roles that RNA molecules play, they have been called the Swiss army knives of the cellular world .
    ::RNA是一个非常多用途的分子,在生命中扮演着多重角色。 比如,除了帮助制造蛋白质之外,还有调节基因表达的RNA分子,以及催化维持生命所需的其他RNA分子。 由于RNA分子所扮演的角色多种多样,它们被称作“细胞世界的瑞士军队刀 ” 。

    It's an RNA World
    ::这是一个RNA世界

    The function of DNA is to store genetic information inside cells. It does this job well, but that's about all it is can  do. DNA can't act as an , for example, to catalyze biochemical reactions that are needed to keep us alive. Proteins are needed for this and many other life functions. Proteins work exceptionally well to keep us alive, but they are unable to store genetic information. Proteins need DNA for that. Without DNA, proteins could not exist. On the other hand, without proteins, DNA could not survive. This poses a chicken-and- egg sort of problem: Which evolved first? DNA or proteins?
    ::DNA的功能是将基因信息存储在细胞内部。 它的工作做得很好, 但这就是它所能做的。 DNA不能起到催化生物化学反应的作用, 例如, 催化我们生存所需的生物化学反应。 需要蛋白质来维持这个功能和许多其他生命功能。 蛋白质的工作非常出色, 但却无法保存基因信息。 蛋白质需要DNA。 没有DNA, 蛋白质就无法存在。 另一方面, 没有蛋白质, DNA就无法生存。 这造成了一种鸡蛋白质问题: 哪种进化先进? DNA还是蛋白质?

    Some scientists think that the answer is neither. They speculate instead that RNA was the first biochemical to evolve. The reason? RNA can do more than one job. It can store information as DNA does. It can also perform various jobs (such as catalysis) to keep cells alive, as proteins do. The idea that RNA was the first biochemical to evolve, predating both DNA and proteins, is called the RNA world hypothesis . According to this hypothesis , billions of years ago, RNA molecules evolved that could both survive and make copies of themselves. According to the hypothesis, early RNA molecules eventually evolved the ability to make proteins, and at some point RNA mutated to form DNA. 
    ::一些科学家认为答案是两者都不是。他们相反地猜测RNA是第一个进化的生化物。原因如下:RNA可以做不止一项工作。它可以像DNA那样存储信息。它也可以像蛋白质一样从事各种工作(比如催化)来保持细胞的活性。RNA是第一个进化的生化物,先于DNA和蛋白质,这个想法被称为RNA世界假设。根据这个假设,数十亿年前,RNA分子就进化了,既能生存又能复制自己。根据这个假设,早期RNA分子最终演变了产生蛋白质的能力,在某个时候,RNA变异了形成DNA的能力。

    Feature: Reliable Sources
    ::特征:可靠来源

    The RNA world hypothesis has not gained enough support in the scientific community to be accepted as a . In fact, there are probably as many detractors as supporters of the hypothesis. Do a w eb search  to learn more about the RNA world hypothesis and the evidence and arguments both for and against it. When weighing the information you gather, consider the likely reliability of the different Web sites you visit. B ased on what you determine  are the most reliable sources and the most convincing arguments ,  form your own opinion about the hypothesis. You may decide to accept or reject the hypothesis. Alternatively, you may decide to reserve judgement until  —  or if  —  more evidence or arguments are forthcoming.
    ::RNA世界假设在科学界没有得到足够的支持,无法被接受为一种假设。事实上,很可能有尽可能多的诋毁者支持这一假设。在网上搜索以了解更多关于RNA世界假设以及证据和论据以及与之相反的论据。在权衡你收集的信息时,考虑你访问的不同网站可能具有的可靠性。根据你确定的最可靠来源和最令人信服的论据,就这一假设形成你自己的意见。你可以决定接受或拒绝这一假设。或者,你可以决定保留判断,直到有更多的证据或论据出现。

    Summary
    ::摘要

    • The central dogma of molecular biology can be summed up as: DNA → RNA → Protein. This means that the genetic instructions encoded in DNA are first transcribed to RNA, and then from RNA they are translated into a protein.
      ::分子生物学的核心教条可以概括为:DNA RNA Protein。 这意味着DNA编码的基因指示首先被转录到RNA,然后从RNA转换成蛋白质。
    • Like DNA, RNA is a nucleic acid. Unlike DNA, RNA consists of just one polynucleotide chain instead of two, contains the base uracil instead of thymine, and contains the sugar ribose instead of deoxyribose.
      ::与DNA一样,RNA是一种核酸。 与DNA不同,RNA只包含一个聚核酸链,而不是两个链,包含基体毫升,而不是胸腺,并含有糖肋骨而不是脱氧核糖。
    • The main function of RNA is helping to make proteins. There are three main types of RNA involved in protein synthesis: messenger RNA (mRNA), ribosomal RNA (rRNA), and transfer RNA (tRNA). RNA has additional functions, including regulating gene expression and catalyzing other biochemical reactions.
      ::RNA的主要功能是帮助制造蛋白质,在蛋白质合成中,RNA主要有三种类型:信使RNA(mRNA)、RNA(rRNA)和RNA(tRNA),RNA还有其他功能,包括调节基因表达和催化其他生化反应。
    • According to the RNA world hypothesis, RNA was the first type of biochemical molecule to evolve, predating both DNA and proteins. The hypothesis is based mainly on the multiple functions of RNA, which can store genetic information like DNA and carry out life processes (like proteins).
      ::根据RNA世界假设,RNA是第一种先于DNA和蛋白质的进化生化分子,主要基于RNA的多重功能,RNA可以储存DNA等遗传信息并进行生命过程(如蛋白质 ) 。

    Review
    ::回顾

    1. State the central dogma of molecular biology.
    ::1. 说明分子生物学的中心教条。

    2. Compare and contrast the structure and function of DNA and RNA.
    ::2. 比较和比较DNA和RNA的结构和功能。

    3. Identify the three main types of RNA needed to synthesize a protein. What role is played by each type of RNA in this process?
    ::3. 确定合成蛋白质所需的三种主要RNA类型:每种RNA在这一过程中发挥什么作用?

    4. What is the RNA world hypothesis? What is the main argument that supports it ?
    ::4. RNA世界假设是什么?支持它的主要论点是什么?

    5. RNA is ________ from DNA, and then ________ into protein.
    ::5. RNA来自DNA,然后是蛋白质。

    a. transformed; transfigured
    ::a. 变形;变形

    b. transfigured; transformed
    ::b. 变形;变形

    c. transcribed; translated
    ::c. 转录;翻译

    d. translated; transcribed
    ::d. 翻译;转录

     

    6. Which type of RNA (mRNA, rRNA, or tRNA) best fits each of the statements below? Choose only one type for each.
    ::6. 哪种RNA(mRNA、RRNA或tRNA)最适合以下每种语句?选择一种。

    a. leaves the nucleus through nuclear pores
    ::a. 将核核核子通过核孔

    b. helps form the structure where proteins are assembled
    ::b. 帮助形成蛋白质组装结构

    c. transports the building blocks of proteins
    ::c. 运输蛋白质的组成部分

     

    7. What are the building blocks of proteins?
    ::7. 蛋白质的组成部分是什么?

    a. DNA
    ::a. DNA

    b. RNA
    ::b. RNA

    c. amino acids
    ::c. 氨基酸

    d. ribosomes
    ::d. 血压

     

    8. True or False:  RNA is the middle step in the central dogma of molecular biology.
    ::8. 真实或假:RNA是分子生物学核心教条的中间步骤。

     

    9. True or False:  RNA contains the genetic instructions that direct the assembly of DNA.
    ::9. 真实或假:RNA含有指导DNA组装的遗传指示。

     

    10. True or False:  An RNA molecule consists of a single nucleotide.
    ::10. 真实或假:RNA分子由单核酸组成。

     

    11. In DNA, the base thymine binds to the base adenine. In RNA, does thymine bind to adenine? Why or why not?
    ::11. 在DNA中,基底的甲状腺与基的结合,在RNA中,甲状腺与结合吗?为什么或为什么没有?

     

    12. Why do you think the central dogma of molecular biology is so important to the study of life?
    ::12. 为什么你认为分子生物学的中心教条 对生命研究如此重要?

     

    13. Ribosomes are located in the ______________ of the cell.
    ::13. Riboomes位于囚室的________。

     

    14. The sugar in RNA is called _________ .
    ::14. RNA的糖称为_________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

    Explore More
    ::探索更多

    RNA may have been the origin of life on Earth. In this video, explore RNA's evolving role over the course of  billions of years of evolutionary history: 
    ::RNA可能是地球上生命的起源。在这个视频中,探索RNA在数十亿年进化史中不断演变的作用:

    In order to better understand the process of protein synthesis, check out this video comparing  DNA and RNA:  
    ::为了更好地了解蛋白质合成过程,