章节大纲

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    Blueprint of a house with drafting tools, illustrating instructions for building.

    Where's the instructions?
    ::指示在哪?

    How do your cells know what to do? Just like builders have blueprints to tell them how to build a house, your cells also have instructions. Your cells' instructions are molecules of DNA.
    ::你的细胞如何知道该怎么做?就像建筑者有蓝图告诉他们如何建造房子一样, 你的细胞也有指示。你的细胞指示是DNA的分子。

    What is DNA?
    ::DNA是什么? DNA吗? What is DNA?

    DNA is the material that makes up our chromosomes and stores our genetic information. When you build a house, you need a blueprint, a set of instructions that tells you how to build. The DNA is like the blueprint for living organisms . The genetic information is a set of instructions that tell your cells what to do.
    ::DNA是构成我们的染色体和储存我们的遗传信息的材料。当你建房时,你需要一个蓝图,一套指示你如何建房的指示。DNA就像活生物体的蓝图。基因信息是一套指示,指示你的细胞该怎么做。

    DNA is an abbreviation for deoxyribonucleic acid . As you may recall, nucleic acids are a type of macromolecule that store information. The deoxyribo part of the name refers to the name of the sugar that is contained in DNA, deoxyribose. DNA may provide the instructions to make up all living things, but it is actually a very simple molecule . DNA is made of a very long chain of nucleotides . In fact, in you, the smallest DNA molecule has well over 20 million nucleotides.
    ::DNA是脱氧核糖核酸的缩写。 正如你可能记得的那样,核糖核酸是一种储存信息的大型分子。 名称中的脱氧核糖核酸部分指的是DNA中含有的糖的名称, 脱氧核糖核酸。 DNA可以提供所有生物组成的指示, 但实际上它是一个非常简单的分子。 DNA是由很长的核糖核酸链组成的。 事实上, 在你身上,最小的DNA分子有2 000多万核糖核酸。

     

     

    Nucleotides
    ::核分子

    Nucleotides are composed of three main parts:
    ::核糖核酸由三个主要部分组成:

    1. a phosphate group.
      ::a 磷酸盐类。
    2. a 5-carbon sugar (deoxyribose in DNA).
      ::a 5碳糖(脱氧核糖核酸)。
    3. a nitrogen-containing base.
      ::a 含氮基数。

    The only difference between each nucleotide is the identity of the base. There are only four possible bases that make up each DNA nucleotide: adenine (A), guanine (G), thymine (T), and cytosine (C).
    ::每一种核核酸之间的唯一区别是基点的身份。 每种DNA核酸只有四种可能的基点组成:阿丁(A)、谷氨(G)、胸腺(T)和cytosine(C)。

    The Genetic Code
    ::《遗传法》

    The various sequences of the four nucleotide bases make up the genetic code of your cells. It may seem strange that there are only four letters in the “alphabet” of DNA. But since your chromosomes contain millions of nucleotides, there are many, many different combinations possible with those four letters.
    ::四个核糖酸基底的不同序列组成了细胞的遗传代码。 DNA的“ 阿尔法贝特” 中只有四个字母似乎很奇怪。 但既然你的染色体含有数百万核酸,那么这四个字母就有很多不同的组合。

    But how do all these pieces fit together? James Watson and Francis Crick won the Nobel Prize in 1962 for piecing together the structure of DNA. Together with the work of Rosalind Franklin and Maurice Wilkins, they determined that DNA is made of two strands of nucleotides formed into a double helix , or a two-stranded spiral, with the sugar and phosphate groups on the outside, and the paired bases connecting the two strands on the inside of the helix ( Figure ).
    ::但所有这些片段是如何组合在一起的呢?詹姆斯·沃森和弗朗西斯·克里克1962年因混合DNA结构而获得诺贝尔奖。他们与罗莎琳德·富兰克林和莫里斯·威尔金斯一起确定,DNA是由两股核素组成的DNA组成,形成双螺旋,或两层螺旋,外部有糖和磷酸盐组,以及连接螺旋(Figure ) 内两根线的对齐基。

    Representation of DNA's double helix structure with nucleotide bases and sugar-phosphate backbone.
    DNA’s three-dimensional structure is a double helix. The hydrogen bonds between the bases at the center of the helix hold the helix together.

    Base-Pairing
    ::基地对等

    The bases in DNA do not pair randomly. When Erwin Chargaff looked closely at the bases in DNA, he noticed that the percentage of adenine (A) in the DNA always equaled the percentage of thymine (T), and the percentage of guanine (G) always equaled the percentage of cytosine (C). Watson and Crick’s model explained this result by suggesting that A always pairs with T, and G always pairs with C in the DNA helix. Therefore A and T, and G and C, are "complementary bases," or bases that always pair together, known as a base-pair . The base-pairing rules state that A will always bind to T, and G will always bind to C ( Figure ). For example, if one DNA strand reads ATGCCAGT, the other strand will be made up of the complementary bases: TACGGTCA.
    ::DNA中的基数并不是随机对齐的。 当Erwin Doffaff仔细观察DNA中的基数时,他注意到DNA中的(A)的百分比总是等于胸腺(T)的百分比,而guanine(G)的百分比总是等于细胞素(C)的百分比。 华生和克瑞克的模型解释了这一结果,暗示A总是与T对齐,G总是在DNA螺旋中与C对对齐。 因此,A和T以及G和C是“补充基数 ” , 或总是对齐的基数,被称为基数。 基数规则规定,A将永远与T捆绑在一起,G将永远与C(Figure ) 捆绑在一起。 例如,如果一个DNA直线读ATGCATT,另一根就会由补充基数组成:TACGGTCA。

    Hydrogen bonds hold the complementary bases together, with two bonds forming between an A and a T, and three bonds between a G and a C.
    ::氢债券拥有互补基础,A和T之间有2个债券,G和C之间有3个债券。

    DNA structure with base-pairing between adenine, thymine, guanine, and cytosine.
    The chemical structure of DNA includes a chain of nucleotides consisting of a 5-carbon sugar, a phosphate group, and a nitrogen base. Notice how the sugar and phosphate group form the backbone of DNA (strands highlighted in pink), with the hydrogen bonds between the bases joining the two strands.

    Summary
    ::摘要

    • DNA stores the genetic information of the cell in the sequence of its 4 bases: adenine, thymine, guanine, and cytosine.
      ::DNA储存细胞的遗传信息,按其4个基数的顺序排列:adenine、anmine、guanine和cytosine。
    • DNA is made of a long chain of nucleotides consisting of a 5-carbon sugar, a phosphate group, and nitrogen-containing base.
      ::DNA是由由5碳糖、磷酸盐类和含氮基组成的一长串核糖类链组成的长链核糖类DNA制成。

    Explore More
    ::探索更多

    Use the resource below to answer the questions that follow. Some resources require flash player to view but are not necessary to answer the questions. 
    ::使用下面的资源回答下面的问题,有些资源需要闪电播放器观看,但不必回答问题。

    1. Where is nuclear DNA located in a eukaryotic organism?
      ::核DNA在哪里 位于一个自来水生物体?
    2. Describe the structure of DNA.
      ::描述DNA的结构。
    3. What is another name for the "sentences" that DNA encodes?
      ::DNA编码中的"判决"又叫什么来着?
    4. What do genes tell a cell to do?
      ::基因让细胞做什么?
    5. How long does it take a human cell to copy the DNA in its nucleus before it divides?
      ::人类细胞在分裂之前 需要多久才能复制核中的DNA?
    6. How many new cells does your body produce every day?
      ::你的身体每天产生多少个新细胞?
    7. What steps does the cell take to speed the rate of DNA replication?
      ::细胞采取什么步骤来加速DNA复制速度?

    Review
    ::回顾

    1. Describe the structure of DNA.
      ::描述DNA的结构。
    2. What does a nucleotide consist of?
      ::核糖核酸是什么成分?
    3. What are the base-pairing rules?
      ::基本接线规则是什么?
    4. If one DNA strand reads CCGTAATGCAT, what will be the sequence of the complimentary strand?
      ::如果一个DNA链读CCGTAATGCAT, 补充链的顺序是什么?