Section outline

  • General

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  • DNA DNA

    What you will learn
    ::你会学到什么

    • Important conducted by scientists to determine the nature of genetic material
      ::科学家为确定遗传物质性质而进行的重要研究
    • Establishment of DNA as the genetic material
      ::将DNA确定为遗传物质
    • Timeline of the major discoveries related to DNA structure and its function
      ::与DNA结构及其功能有关的主要发现时间表

    A stylized representation of DNA double helix with colorful base pairs.

    What type of organic molecule is this?
    ::这是什么类型的有机分子?

    Here’s a hint: molecules like this one determine who you are. They contain genetic information that controls your characteristics. They determine your eye color, facial features, and other physical attributes. What molecule is it?
    ::这里有一个提示:像这样的分子决定你是谁。 它们包含控制你特征的遗传信息。 它们决定你的眼睛颜色、面部特征和其他物理属性。 它是什么分子?

    You probably answered "DNA." Today, it is commonly known that DNA is the genetic material. For a long time, scientists knew such molecules existed. They were aware that genetic information was contained within organic molecules . However, they didn’t know which type of molecules play this role. In fact, for many decades, scientists thought that were the molecules that carry genetic information. 
    ::你可能回答“DNA ” 。 今天,众所周知,DNA是遗传物质。 长期以来,科学家们知道这些分子的存在。 他们知道基因信息包含在有机分子中。 但是,他们不知道什么类型的分子可以发挥这种作用。 事实上,几十年来,科学家们一直认为分子是含有基因信息的分子。

    DNA, the Genetic Material
    ::DNA、遗传材料

    DNA, deoxyribonucleic acid, is the genetic material in your . It was passed on to you from your parents and determines your characteristics. The discovery that DNA is the genetic material was another important milestone in molecular biology .
    ::DNA,脱氧核糖核糖核酸, 就是你体内的遗传物质。它从你父母那里传给你, 并且决定你的特点。发现DNA是遗传物质是分子生物学中的另一个重要里程碑。

    Griffith Searches for the Genetic Material
    ::Griffith 遗传材料搜索

    Many scientists contributed to the identification of DNA as the genetic material. In the 1920s, Frederick Griffith made an important discovery. He was studying two different strains of a , called R (rough) strain and S (smooth) strain. He injected the two strains into mice. The S strain killed (virulent) the mice, but the R strain did not (non-virulent). Griffith also injected mice with S-strain bacteria that had been killed by heat. As expected, the killed bacteria did not harm the mice. However, when the dead S-strain bacteria were mixed with live R-strain bacteria and injected, the mice died. 
    ::1920年代,弗雷德里克·格里菲斯(Frederick Griffith)发现了一个重要的发现。他正在研究两种不同的菌株,一种叫R(槽)菌株和S(鼻)菌株。他把这两种菌株注入小鼠体内。S(病毒)菌株杀死了小鼠,但R(病毒)没有(病毒)菌株。格里菲斯也向小鼠注入了被热力杀死的斯丁基细菌。正如预期的那样,被杀死的细菌并没有伤害小鼠。然而,当死斯丁基菌菌与活体R-strain细菌混合并注射时,小鼠死亡。

    Results of Griffith's experiment on mice with different bacterial strains.
    Griffith’s Experiment

     

    DID YOU KNOW?
    ::你知道吗?

    Griffith used strains of pneumococcus bacteria for his experiments because he was interested in finding a vaccine against these . These bacteria caused millions of deaths by causing pneumonia as a secondary infection during the 1918 pandemic .
    ::Griffith在实验中使用了肺炎球菌菌菌株,因为他有兴趣找到一种疫苗来防治这些菌株。这些细菌在1918年的大流行病期间造成肺炎作为二级感染,造成数百万人死亡。

     

    Based on his observations , Griffith deduced that something in the killed S strain was transferred to the previously harmless R strain, making the R strain deadly. He called this process transformation, as something was "transforming" the bacteria from one strain into another strain. What was that something? What type of substance could change the characteristics of the organism that received it?
    ::根据他的观察,格里菲斯推论,被杀死的S菌株中有什么东西被转移到了先前无害的R菌株,使R菌株致命。他称这一过程转型为“将细菌从一个菌株“转化成另一个菌株 ” 。那是什么?哪种物质可以改变获得该菌株的生物的特性?

    Avery’s Team Makes a Major Contribution
    ::Avery的团队做出了重大贡献

    In the early 1940s, a team of scientists led by Oswald Avery tried to answer the question raised by Griffith’s results. Avery, together with his colleagues Colin MacLeod and Maclyn McCarty, inactivated various substances in the heat-killed S-strain bacteria. They then mixed the heat-killed S-strain bacteria with the harmless R-strain bacteria. When proteins and were inactivated, the R-strain still transformed into the deadly S-strain. This ruled out proteins and RNA as the genetic material. Why? Even without the S-strain proteins or RNA, the R-strain was changed or transformed, into the deadly S-strain. However, when the researchers inactivated DNA in the S-strain, the R-strain did not transform. This led to the conclusion that DNA is the substance that controls the characteristics of organisms. In other words, DNA is the genetic material.   
    ::1940年代初期,由奥斯瓦尔德·艾弗里领导的一组科学家试图回答格里菲斯的研究结果提出的问题。艾弗里和他的同事科林·麦克莱德和麦克林·麦卡蒂一起,在热杀菌的S-S-S-S-Srain细菌中停止了各种物质的活动。他们随后把热杀S-S-strain细菌与无害的R-strain细菌混合起来。当蛋白质和被激活时,R-S-S-S-strain仍然转化成致命的S-S-strain细菌。这排除了蛋白质和RNA作为遗传材料。为什么?即使没有S-S-strain蛋白或RNA,R-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-Serent,R-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-s,RNA,RNA,RNA,R-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-S-

    Flowchart showing the Avery-MacLeod-McCarty experiment results with inactivated proteins, RNA, and DNA.
    The Avery-MacLeod-McCarty Experiment

     

    DID YOU KNOW?
    ::你知道吗?

    Even after Avery and his team’s experiments showed that DNA was the genetic material, the scientific community was skeptical. They thought that a molecule of DNA was too simple to carry genetic information while proteins were considered complex enough to be the genetic material.
    ::即使在Avery及其团队的实验表明DNA是遗传物质之后,科学界还是持怀疑态度。 他们认为DNA分子太简单,无法携带遗传信息,而蛋白质则被认为复杂到可以成为遗传物质。

     

    Hershey and Chase Seal the Deal
    ::赫希和大通达成交易

    The conclusion that DNA is the genetic material was not widely accepted at first. It had to be confirmed by other research. In the 1950s, Alfred Hershey and Martha Chase did experiments with known as bacteriophages , a virus that infects bacteria, and bacteria. Viruses are not made of cells. Bacteriophages are basically DNA inside a protein coat. To reproduce, a virus must insert its own genetic material into a cell (such as a bacterium). Then it uses the cell’s machinery to make more viruses. The researchers used different radioactive elements to label the DNA and proteins in viruses. This allowed them to identify which molecule the viruses inserted into bacteria. DNA was the molecule they identified. This confirmed that DNA is the genetic material.
    ::DNA是基因材料这一结论一开始并未得到广泛接受。 它必须得到其他研究的证实。 1950年代, Alfred Hershey 和 Martha Chase 对细菌进行了实验, 细菌是一种感染细菌和细菌的病毒。 病毒不是细胞制造的。 细菌基本上是蛋白外衣中的DNA。 要繁殖, 病毒必须将其基因材料插入细胞( 如细菌 ) 。 然后, 病毒必须使用细胞的机器制造更多的病毒。 研究人员使用不同的放射性元素来给病毒中的DNA和蛋白质贴上标签。 这使得他们能够识别细菌中的哪种分子病毒。 DNA是他们识别的分子。 这证实了DNA是遗传物质。

    The Hershey and Chase Experiment
    ::赫希和大通实验

    BATCH 1 BATCH 2
    Bacteriophage infecting bacteria, demonstrating that only DNA enters the cell, not protein.
    Conclusion - Proteins are not the genetic material.
    Timeline of research showing DNA as genetic material, including bacteriophage and bacterial infection.
    Conclusion - DNA is the genetic material.

     

    Shown in the Figure is a timeline of t he work of several researchers that led to the establishment of DNA as the genetic material followed by the discovery of its structure.
    ::图中显示了数名研究人员的工作时间表,导致将DNA确定为遗传材料,然后发现其结构。

    DNA Discovery Timeline
    ::DNA 发现时间线

    Timeline showing key experiments that established DNA as the genetic material.

    Summary

    • DNA, deoxyribonucleic acid, is the genetic material in your cells. It was passed on to you from your biological parents and determines your characteristics.
      ::DNA,脱氧核糖核糖核酸,是细胞中的遗传物质。它从你的亲生父母传给你,决定了你的特性。
    • For many decades, scientists thought that proteins were the molecules that carry genetic information.
      ::数十年来,科学家一直认为蛋白质是含有遗传信息的分子。
    • The work of several researchers led to the discovery that DNA is the genetic material.
      ::若干研究人员的工作导致发现DNA是遗传物质。
    • Along the way, Griffith discovered the process of transformation.
      ::沿着这条路,格里菲斯发现了转变的过程。

    Review Questions

    1. List the research that determined that DNA is the genetic material.
      ::列出确定DNA是遗传物质的研究清单。
    2. What is transformation?
      ::什么是转变?
    3. What happened to the R-strain bacteria when Avery and his colleagues inactivated DNA in the S strain bacteria?
      ::当Avery和他的同事在S菌株中 激活DNA时 R-strain细菌呢?