章节大纲

  • 常规

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  • 代谢与复制

    A DNA double helix structure illustrating genetic information transfer.

     

    What is an RNA world?
    ::什么是RNA世界?

    DNA passes most genetic information today. But some scientists think that for the first life on Earth, genetic information was passed by RNA. They call this the  RNA world hypothesis .
    ::今天,DNA传递了大部分基因信息。但有些科学家认为,对于地球上的第一生命来说,基因信息是由RNA传递的。他们称之为RNA世界假设。

    Metabolism
    ::新陈代谢

    Organic  molecules must carry out the chemical work of cells. This is their  metabolism . Living organisms need chemical reactions to live, grow, and reproduce. The chemical reactions occur in sequences of steps. These sequences are known as metabolic pathways. The metabolic pathways are very similar for all life on Earth. That includes single celled bacteria that have been around for billions of years. It includes the most complex life forms on Earth today. What does it mean that the metabolic pathways are so similar for all life? This means that the metabolic pathways evolved very early in Earth's history.
    ::有机分子必须执行细胞的化学工作。 这是它们的新陈代谢。 活生物体需要化学反应才能生存、 生长和繁殖。 化学反应是按步骤顺序发生的。 这些序列被称为代谢途径。 这些代谢途径对地球上的所有生命来说非常相似。 包括了数十亿年左右的单细胞细菌。 它包括了今天地球上最复杂的生命形式。 代谢途径对所有生命来说都如此相似意味着什么? 这意味着代谢途径在地球历史上很早就演变了。

    Replication
    ::复制复制

    Living cells need organic molecules, known as  nucleic acids . Nucleic acids are molecules that store genetic information. They pass that genetic information to the next generation. Deoxyribonucleic acid (DNA) is the nucleic acid that carries information for nearly all living cells today. DNA has done this for most of Earth's history. Ribonucleic acid (RNA) delivers genetic instructions to the   in a cell where  protein  is synthesized. RNA regulates protein synthesis. Some scientists think that RNA was the first replicating  molecule .
    ::活细胞需要有机分子,即核糖核酸。核酸是存储遗传信息的分子。它们将遗传信息传递给下一代。脱氧核糖核酸(DNA)是今天几乎所有活细胞都携带信息的核酸。DNA是地球上大部分历史的代名词。核糖核酸(RNA)向蛋白合成的细胞提供遗传指令。RNA管理蛋白合成。一些科学家认为RNA是第一个复制分子。

    A segment of DNA that is inheritable is a  gene . Every organism has a collection of genes that code for the traits that organism could have. Not all genes are expressed; therefore, knowing all of your genes does not tell you exactly who you are.
    ::DNA中可以继承的部分是一种基因。每个生物都有一系列基因,这些基因可以编码生物的特性。并非所有的基因都表达出来;因此,了解你的所有基因并不能说明你到底是谁。

    Summary
    ::摘要

    • An organism's metabolism is the chemical reactions that allow it to live, grow, and reproduce.
      ::有机体的新陈代谢是化学反应 允许它生存、生长和繁殖
    • Nucleic acids pass genetic information to the next generation.
      ::核酸将遗传信息传给下一代。
    • DNA passes genetic information for living cells. RNA passes genetic information for protein synthesis.
      ::RNA通过基因信息进行蛋白质合成。

    Review
    ::回顾

    1. What is the purpose of an organism's metabolism?
      ::生物体的新陈代谢的目的是什么?
    1. What are metabolic pathways?
      ::什么是代谢途径?
    1. Metabolic pathways are similar between very simple and very complex organisms. What do scientists think this means?
      ::在非常简单和非常复杂的生物中,代谢途径相似。 科学家们认为这意味着什么?
    1. What do nucleic acids do?
      ::核酸会做什么?
    1. What are the two nucleic acids and what does each do?
      ::两种核酸是什么? 每种酸都做什么?
    1. If you have a gene for a purple nose, but you don't in fact have a purple nose, what do scientist say about that gene?
      ::如果你有紫鼻子的基因,但你实际上没有紫鼻子, 科学家会怎么说这个基因?

    Explore More
    ::探索更多

    Use the resource below to answer the questions that follow.
    ::利用以下资源回答以下问题。

    1. Where are virtually all of your genes?
      ::你的所有基因都在哪里?
    1. What are genes?
      ::什么是基因?
    1. Describe the structure of a DNA molecule.
      ::描述DNA分子的结构。
    1. What do the four bases—adenine (A), thymine (T), cytosine (C), and guanine (G)—do?
      ::四个基数--九(A)、四(T)、七(C)和五(G)--是做什么的?
    1. What are chromosomes made of?
      ::什么是染色体?
    1. How many chromosomes do humans have?
      ::人类有多少染色体?
    1. How similar are we to chimps? How similar to other humans?
      ::我们和黑猩猩有多相似?