章节大纲

  • 常规

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  • 《遗传法》

    What will you learn
    ::你会学到什么

    • What is the genetic code
      ::遗传法是什么?
    • How the genetic code is read
      ::基因代码是如何读取的
    • The characteristics of the genetic code
      ::遗传法的特征

    DNA strands overlaid on a colorful representation of the genetic code.

    How do you go from four letters to 20 amino acids?
    ::你如何从4个字母到20个氨基酸?

    You need a code. And the code that changes the information embedded in and into ordered amino acids and is the genetic code. And every living organism uses the same genetic code.
    ::你需要一个代码。这个代码可以改变 嵌入和嵌入有顺序的氨基酸的信息 并且是基因代码。每个生物都使用相同的遗传代码。

    The Genetic Code
    ::《遗传法》

    How is the information in a gene encoded? The answer is the genetic code. The genetic code consists of the sequence of nitrogen bases—A, C, G, U—in an mRNA chain. 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. 
    ::在基因编码中,信息是如何编码的?答案是基因代码。遗传代码包括氮基的序列-A、C、G、U-在一个 mRNA链中。四个基组成基因代码的“字母 ” 。字母分为三组组成代号“ 字 ” , 称为“ codons ” 。 每一个codon代表一种氨基酸(encodes ) , 除非它为开始或停止信号编码 。

    There are 20 common amino acids in proteins. There are 64 possible codons, more than enough to code for the 20 amino acids. The genetic code is shown in the  Figure . 
    ::蛋白质中共有20种常见的氨基酸。有64种可能的codon,足以对20种氨基酸进行编码。图中显示了遗传代码。

    Table of the genetic code showing codons, amino acids, and start/stop signals.
    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.

    Reading the Genetic Code
    ::阅读《遗传法》

    As shown in the  Figure , the codon AUG codes for the amino acid methionine. This codon is also the start codon that begins . The start codon establishes the reading frame of mRNA. The reading frame is the way the letters are divided into codons. After the AUG start codon, the next three letters are read as the second codon. The next three letters after that are read as the third codon, and so on. The mRNA molecule 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. Stop codons are also known as termination codons. 
    ::如图所示,氨基酸甲硫磷的codon AUG编码。该codon 也是开始的开始codon。开始codon 建立了 mRNA的读数框架。读数框架是字母分为codon 的方式。在 AUG 开始codon 之后,接下来的3个字母被解读为第二个codon。后面的3个字母被解读为第三个codon,等等。 mRNA 分子被读取, 以codon 连接, 直到到达一个停止 Codon。 UAG、 UGA 和 UAA A都是停止的codon 。 它们不为任何氨基酸编码。 停止codon 也被称为终止 Codon。

    Can you match the amino acids to the codons?
    ::你能把氨基酸和海豚酸配对吗?

     

    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 organisms use the same genetic code. This shows that all organisms share a common evolutionary history.
      ::遗传法是普遍的,所有已知的生物都使用相同的遗传法,这表明所有生物都有共同的进化历史。
    • The genetic code is unambiguous. Each codon codes for just one amino acid (or start or stop). What might happen if codons encoded more than one amino acid?
      ::遗传代码是明确的。 每种codon代码仅代表一种氨基酸( 或开始或停止 ) 。 如果codon编码超过一种氨基酸, 会发生什么?
    • The genetic code is redundant. Most amino acids are encoded by more than one codon. In the  Figure , how many codons code for the amino acid threonine? What might be an advantage of having more than one codon for the same amino acid?
      ::基因代码是多余的。 大部分氨基酸都由不止一个codon编码。 在图中, 氨基酸血清有多少codon代码? 拥有一个以上codon的同一氨基酸的好处是什么?

       

     

     

     

     

    Summary
    ::摘要

    • The genetic code consists of the sequence of bases in DNA or RNA.
      ::遗传代码包括DNA或RNA中基数的顺序。
    • Groups of three bases form codons, and each codon stands for one amino acid (or start or stop).
      ::3个基底组构成codon, 每个codon代表一种氨基酸( 开始或停止) 。
    • The codons are read in sequence following the start codon until a stop codon is reached.
      ::鳕鱼在开始后按顺序阅读,直到达到停止的鳕鱼。
    • The genetic code is universal, unambiguous, and redundant.
      ::遗传法是普遍、明确和多余的。

    Review
    ::回顾

    1. What is the genetic code?
      ::遗传密码是什么?
    2. What are codons? How many codons are there?
      ::什么是海豚,有多少海豚?
    3. Use the genetic code to translate the following segment of RNA into a sequence of five amino acids: GUC-GCG-CAU-AGC-AAG
      ::使用遗传编码将RNA的以下部分转化为五种氨基酸的序列:GUC-GCG-CAU-AGC-AAAG
    4. The genetic code is universal, unambiguous, and redundant. Explain what this means.
      ::基因密码是通用的 明确的 多余的 解释一下这意味着什么