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  • 《遗传法》

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    Can You Code?
    ::你懂法典吗?

    If someone asks you whether you can code, you probably assume they are referring to computer code. The image above represents an important code that you use all the time — but not with a computer! It's the genetic code, and it is used by your to store information, as well as to make and .
    ::如果有人问您您能否编码, 您可能认为他们指的是计算机编码。 上面的图像代表了您一直使用的重要代码, 而不是计算机! 这是遗传代码, 您用来存储信息, 以及制作和制作 。

    What Is the Genetic Code?
    ::什么是遗传法?

    The  genetic code consists of the sequence of nitrogen bases in a polynucleotide chain of or RNA. The bases are adenine (A), cytosine (C), guanine (G), and thymine (T) (or uracil, U, in RNA). The four bases make up the “letters” of the genetic code. The letters are combined in groups of three to form code “words,” called codons . Each codon stands for (encodes) one amino acid , unless it codes for a start or stop signal. There are 20 common amino acids in proteins. With four bases forming three-base codons, there are 64 possible codons. This is more than enough to code for the 20 amino acids. The genetic code is shown in the table .
    ::遗传代码由多种核素酸链或RNA的氮基序列组成。 基数是( A)、 cytosine ( C)、 guanine ( G) 和 ymine ( T) ( 或 uracil, U , 在 RNA 中 ) 。 四个基数构成基因代码的“ 字母 ” 。 字母分为三组组成代号“ 字 ” , 称为codons 。 每个codon 代表一种氨酸( encodes) , 除非它为开始或停止信号编码 。 蛋白质中共有20种氨酸 。 有四个基数组成三基数的codon, 4个基数为64 codon。 这足以为 20 氨酸编码。 基因代码在表格中显示 。

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    The Genetic Code. To find the amino acid for a particular codon, find the cell in the table for the first and second bases of the codon. Then, within that cell, find the codon with the correct third base. For example, CUG codes for leucine, AAG codes for lysine, and GGG codes for glycine.
    ::遗传法。 要找到某一种codon 的氨基酸, 请在 codon 的第一和第二个基点的表格中找到细胞。 然后在这个基点内找到正确的三基点的codon 。 例如, CUG 的 Leucine 代码、 AAG 的赖氨酸代码和 GGG 的甘油代码 。

     

    Reading the Genetic Code
    ::阅读《遗传法》

    If you find the codon AUG in the table , you will see that it codes for the amino acid methionine. This codon is also the start codon that establishes the reading frame of the code. The reading frame is the way the bases are divided into codons. It is illustrated in the figure . After the AUG start codon, the next three bases are read as the second codon. The next three bases after that are read as the third codon, and so on. The sequence of bases is read, codon by codon, until a stop codon is reached. UAG, UGA, and UAA are all stop codons. They do not code for any amino acids.
    ::如果在表格中找到Codon AUG, 你会看到它为氨基酸甲硫磷编码。 这个codon 也是建立代码读数框架的开始codon。 读数框架是将基数分为codons的方式。 图表中显示了这一点。 在 AUG 开始codon 之后, 下三个基数被解读为第二个codon 。 后面三个基数被解读为第三个codon, 等。 基数序列被读取, codon 连接 Codon , 直到达到一个停止的codon。 UAGA、 UGA 和 UAAA 都是停止的codon。 它们不为任何氨酸编码 。

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    Reading the Genetic Code. The genetic code is read three bases at a time. Codons are the code words of the genetic code. Which amino acid does codon 2 in the drawing stand for?
    ::阅读《遗传法》。基因代码一次读三个基数。 Codons是基因代码的代码词。 氨基酸在绘图台中代表哪一种 Codon 2 ?

     

    Characteristics of the Genetic Code
    ::《遗传法》的特点

    The genetic code has a number of important characteristics:
    ::遗传编码有若干重要特征:

    • The genetic code is universal. All known living things have the same genetic code, which shows that all organisms share a common evolutionary history.
      ::基因密码是普遍性的,所有已知生物都有相同的基因编码,这表明所有生物都有共同的进化历史。
    • The genetic code is unambiguous. This means that each codon codes for just one amino acid (or start or stop). This is necessary so there is no question about which amino acid is correct.
      ::遗传代码是明确的。 这意味着每个codon代码只代表一种氨基酸( 或开始或停止 ) 。 这是必要的, 因此毫无疑问氨基酸正确无误 。
    • The genetic code is redundant. This means that each amino acid is encoded by more than one codon. For example, in the table above, four codons code for the amino acid threonine. Redundancy in the code helps prevent errors in . If a base in a codon changes by accident, there is a good chance that it will still code for the same amino acid.
      ::遗传代码是多余的。 这意味着每一个氨基酸都由不止一个codon编码。 例如, 在上表中, 4个codon 代码用于氨基酸血清。 代码中的冗余有助于防止错误。 如果一个codon的基数因意外而变化, 它很有可能仍然对同一种氨基酸进行编码 。

    Cracking the Code
    ::破坏《守则》

    The double helix structure of DNA was discovered in 1953. It took just eight more years to crack the genetic code. The scientist primarily  responsible for deciphering the code was American biochemist Marshall Nirenberg, who worked at the National Institutes of Health in the United States. When Nirenberg began the research in 1959, the manner in which proteins are synthesized in cells was not well understood, and messenger RNA had not yet been discovered. At that time, scientists didn't even know whether DNA or RNA was the molecule used as a template for protein synthesis. Nirenberg, along with a collaborator named Heinrich Matthaei, devised an ingenious to determine which molecule — DNA or RNA — has this important role. They also began deciphering the genetic code.
    ::DNA的双螺旋结构于1953年被发现,仅仅用了8年的时间才破解基因密码。负责解译密码的科学家主要是美国生物化学家Marshall Nirenberg,他在美国国家卫生研究所工作。当Nirenberg于1959年开始研究时,细胞中蛋白质合成的方式还没有得到很好的理解,信使RNA尚未被发现。当时,科学家甚至不知道DNA或RNA是用作蛋白质合成样本的分子。Nirenberg与一个叫Heinrich Matthaei的同僚一起设计了一种巧妙的方法,以确定哪些分子(DNA或RNA)具有这一重要作用。他们也开始破译基因代码。

    Nirenberg and Matthaei added the contents of bacterial cells to each of 20 test tubes. The cell contents provided the necessary "machinery" for the synthesis of a polypeptide molecule. The researchers also added all 20 amino acids to the test tubes, with a different amino acid "tagged" by a radioactive element in each test tube. That way, if a polypeptide formed in a test tube, they would be able to tell which amino acid it contained. Then, they added synthetic RNA containing just one nitrogen base to all 20 test tubes. They used the base uracil in their first experiment. They discovered that an RNA chain consisting only of uracil bases produces a polypeptide chain of the amino acid phenylalanine. This experiment showed that RNA (rather than DNA) is the template for protein synthesis, but it also showed that a sequence of uracil bases codes for the amino acid phenylalanine. The year was 1961, and it was a momentous occasion. When Nirenberg presented the discovery at a scientific conference later that year, he received a standing ovation. As Nirenberg puts it, "...for the next five years I became like a scientific rock star."
    ::在20个测试管中,每个测试管中都添加了细菌细胞的内容。细胞内容为合成聚苯醚分子提供了必要的“机器”。研究人员还在测试管中添加了所有20种氨酸,每个测试管中都有不同的氨酸“塞住”放射性元素。这样,如果在试验管中形成一种聚苯并二酸,他们就能知道其中含有哪些氨酸。然后,他们在所有20个测试管中添加了只包含一个氮基基的合成RNA。他们第一次实验中使用了基质的极拉。他们发现,只有聚氨基基的RNA链条产生了一个氨酸苯丙烯的聚酰胺链条。这一实验表明,氨酸苯丙胺(而不是DNA)是蛋白质合成的模板,但也表明氨酸苯丙胺基底码的序列。1961年,这是一个重要的时刻。当Nirenberg在下一个科学会议上提出发现时,仅由聚氨基质基质基质基质基质组成的RNA链只产生氨酸联苯麻素的聚物链条。这个实验表明,RNA(而不是DNA)是一座恒定的恒星体。

    After Nirenberg and Matthaei cracked the first word of the genetic code, they used similar experiments to show that each codon consists of three bases. Before long, they had discovered the codons for all 20 amino acids. In 1968, in recognition of  this important achievement, Nirenberg was named a co-winner of the in Physiology or Medicine.
    ::在Nirenberg和Matthaei破解了遗传代码的第一个词后,他们用类似的实验来证明每个codon由三个基点组成。不久,他们发现了所有20种氨基酸的codon。1968年,由于认识到这一重要的成就,Nirenberg被命名为生理学或医学的共赢者。

    Summary
    ::摘要

    • The genetic code consists of the sequence of nitrogen bases in a polynucleotide chain of DNA or RNA. The four bases make up the "letters" of the code. The letters are combined in groups of three to form code "words" known as codons, each of which encodes for one amino acid or a start or stop signal.
      ::遗传代码由DNA或RNA的多核核酸链条中的氮基序列组成。 四个基点组成代码的“ 字母 ” 。 字母由三组组成, 组成代号“ 字” , 代号为codons, 每种代号都编码为一种氨基酸或一个开始或停止信号 。
    • AUG is the start codon, and it establishes the reading frame of the code. After the start codon, the next three bases are read as the second codon, the three bases after that as the third codon, and so on until a stop codon is reached.
      ::AUG是开始的codon, 它确定了代码的阅读框架 。 在开始的codon之后, 接下来的3个基点被解读为第二个codon, 之后的3个基点被解读为第三个codon, 等直到达到停止的codon。
    • The genetic code is universal, unambiguous, and redundant.
      ::遗传法是普遍、明确和多余的。
    • The genetic code was cracked in the 1960s, mainly by a series of ingenious experiments carried out by Marshall Nirenberg, who won a Nobel Prize for this achievement.
      ::遗传密码在1960年代破解,主要是马歇尔·尼伦贝格进行的一系列创新实验,他为这一成就获得了诺贝尔奖。

    Review
    ::回顾

    1. Describe the genetic code.
    ::1. 描述遗传编码。

    2. Explain how the genetic code is read.
    ::2. 解释基因编码是如何阅读的。

    3. Identify three important characteristics of the genetic code.
    ::3. 查明遗传编码的三个重要特征。

    4. Summarize how the genetic code was deciphered.
    ::4. 概述遗传编码是如何破译的。

    5. Use the table entitled The Genetic Code, shown , to answer the following questions:
    ::5. 使用题为《遗传法》的表格回答下列问题:

    a. Is the code depicted in the table from DNA or RNA? Explain your reasoning.
    ::a. 表格中的代码是否来自DNA或RNA?

    b. Which amino acid does the codon CAA code for?
    ::b. CAACA代码用于哪一种氨基酸?

    c. What does UGA code for?
    ::c. UGA编码是为了什么?

    d. Look at the codons that code for the amino acid glycine. How many of them are there? How are they similar and different ?
    ::d. 看看氨基酸甘油的编码,其中有多少?它们与哪些相似和不同?

    e. Imagine that you are doing an experiment similar to the one performed by Nirenberg and Matthaei with 20 test tubes, each containing bacterial cell contents and all 20 amino acids, with one type of amino acid labeled in each tube. If you added synthetic RNA containing only the base cytosine, a polypeptide chain consisting of which amino acid would be produced? Explain your answer.
    ::e. 想象一下,你正在做一个类似于Nirenberg和Matthaei进行的实验,试验管有20个测试管,每个测试管内装有细菌细胞内装物和所有20个氨基酸,每个测试管内贴有一种氨基酸标签。如果你添加合成RNA,只包含基细胞素,一个包含氨基酸的聚苯二酸链?解释你的答案。

     

    6. True or False:  One codon can encode for more than one amino acid.
    ::6. 真实或假:一种可编码一种以上的氨基酸的codon。

     

    7. True or False:  The codons for tyrosine in plants are the same as the ones that encode for tyrosine in humans.
    ::7. 真实的或假的:植物中催泪症的codon与人类中催泪症编码的codon相同。

     

    8. True or False:  I n addition to its function establishing where the reading frame starts, t he start codon encodes for an amino acid.
    ::8. 真实或假的:除了确定读数框架起处的功能外,还设定氨基酸的Codon编码起。

     

    9. How many possible codons are there?
    ::9. 有多少可能的共同点?

    a. 64
    ::a. a. 64

    b. 20
    ::b. b. 20

    c. 3
    ::c. 3个

    d. It depends on the species
    ::d. 取决于物种

     

    10. How many common amino acids are there in proteins?
    ::10. 蛋白质中有多少常见氨基酸?

    a. 64
    ::a. a. 64

    b. 20
    ::b. b. 20

    c. 3
    ::c. 3个

    d. 4
    ::d. 4 d. 4

    Explore More
    ::探索更多

    Comparing DNA sequences is vital to understanding evolutionary relationships between organisms. Check out more here: 
    ::比较DNA序列对于理解生物之间的进化关系至关重要。

    Marshall Nirenberg is known in the world of g enetics for cracking the genetic code. Learn more about him here:  
    ::Marshall Nirenberg因破解基因密码而在基因学界中出名。