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  • 核酸

    Who's Who?
    ::谁是谁?

    Without the mustache, it would be difficult to tell the difference between  identical twin astronauts Mark (left) and Scott (right) Kelly. Identical twins like the Kellys show clearly the importance of genes in making us who we are. Genes would not be possible without nucleic acids.
    ::没有胡子,很难区分相同的双胞胎马克(左派)和斯科特(右派)凯利(Scott Kelly)的区别。 Kelly夫妇一样的双胞胎清楚地表明了基因在塑造我们自身中的重要性。没有核酸,基因是不可能实现的。

    What Are Nucleic Acids?
    ::什么是核酸?

    Nucleic acids  are the class of biochemical compounds that includes and . These molecules are built of small monomers called nucleotides . Many nucleotides bind together to form a chain called a  polynucleotide . The nucleic acid DNA (deoxyribonucleic acid) consists of two polynucleotide chains or strands. Thus, DNA is sometimes called double-stranded. The nucleic acid RNA (ribonucleic acid) consists of just one polynucleotide chain or strand, so RNA is sometimes called single-stranded.
    ::核糖核酸是生物化学化合物的类别,包括并包含。这些分子是由称为核糖核酸的小型单体组成的。许多核糖核酸结合成一个称为聚核酸的链条。核酸脱氧核酸(脱氧核糖核酸)由两个多核酸链或线条组成。因此,有时DNA被称为双层。核酸RNA(核糖核酸)只是由一种聚核酸链条或线条组成,因此RNA有时被称为单层。

    Structure of Nucleic Acids
    ::核酸结构

    Each nucleotide consists of three smaller molecules:
    ::每颗核核酸由三个小分子组成:

    1. a sugar molecule (the sugar deoxyribose in DNA and the sugar ribose in RNA)
      ::a 糖分子(DNA中的糖脱氧核糖和RNA中的糖脱氧核糖)
    2. a phosphate group
      ::a 磷酸酯类
    3. a nitrogen base
      ::a 氮基

    If you look at the figure , you can see that the sugar molecule of one nucleotide binds to the phosphate group of the next nucleotide. These two molecules alternate to form the backbone of the nucleotide chain.
    ::如果你看下图,你可以看到一个核糖化物的糖分子与下一个核酸化物的磷酸盐组有关。这两个分子可以互换成核酸化物链的骨干。

    The nitrogen bases in a nucleic acid stick out from the backbone. There are four different nitrogen bases: cytosine, adenine, guanine, and either thymine (in DNA) or uracil (in RNA). In DNA, bonds form between bases on the two nucleotide chains and hold the chains together. Each type of base binds with just one other type of base: cytosine always binds with guanine, and adenine always binds with thymine. These pairs of bases are called complementary base pairs .
    ::核酸中的氮基从脊椎外刺出。 有四个不同的氮基: 细胞素、 腺素、 腺素, 以及胸腺( DNA) 或 尿素( RNA ) 。 在DNA 中, 核酸链中的两个基点之间形成粘结, 并把链子固定在一起。 每一种基点都只与另一种基点捆绑在一起: 细胞素总是与guanine捆绑在一起, 腺素总是与胸腺捆绑在一起。 这些基点被称为互补基底对。

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    Nucleic Acid. Sugars and phosphate groups form the backbone of a polynucleotide chain. Hydrogen bonds between complementary bases hold two polynucleotide chains together.
    ::核心酸:糖类和磷酸盐组构成一个多核酸链的支柱,补充基地之间的氢系将两个多核酸链联在一起。

    The binding of complementary bases causes DNA molecules automatically to take their well-known double helix shape, which is shown in the and animation . A double helix is like a spiral staircase. It  forms naturally and is very strong, making the two polynucleotide chains difficult to break apart.
    ::互补基点的结合自动导致DNA分子以其众所周知的双螺旋形状(这在动画和动画中都可以看到 ) 。 双螺旋就像螺旋楼梯。 它自然形成并且非常强大,使两个多核酸链条难以分解。

    DNA Molecule. Hydrogen bonds between complementary bases help form the double helix of a DNA molecule. The letters A, T, G, and C stand for the bases adenine, thymine, guanine, and cytosine. The sequence of these four bases in DNA is a code that carries instructions for making proteins. Shown is a representation of how the double helix folds into a chromosome.
    ::DNA 分子 分子 。 互补基点之间的氢系有助于形成DNA分子的双螺旋。 字母 A、 T、 G 和 C 代表子宫、 胸腺、 guanine 和 cytosine 。 DNA 中这四个基点的序列是含有蛋白质制作指令的代码。 显示代表双螺旋如何折成染色体 。

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    DNA molecule
    ::DNA分子

    Roles of Nucleic Acids
    ::核酸的作用

    DNA makes up genes, and the sequence of bases in DNA makes up the . Between “starts” and “stops,” the code carries instructions for the correct sequence of amino acids in a . RNA uses the information in DNA to assemble the correct amino acids and help make the protein. The information in DNA is passed from parent cells to daughter cells whenever divide, and it is also passed from parents to offspring when organisms reproduce. This is how inherited characteristics are passed from one generation to the next.
    ::DNA构成基因,而DNA中的基底序列构成DNA。在“起始”和“停止 ” 之间,代码含有氨基酸正确序列的指示。 RNA使用DNA中的信息来组装正确的氨基酸并帮助制造蛋白质。DNA中的信息从父细胞分出时传递给后代细胞,当生物繁殖时,也从父母传给后代。这就是遗传特征如何从一代传到下一代。

    Feature: Human Biology in the News
    ::特著:《新闻》中的人类生物学

    Look at the Neandertals in the image . The painting  is an artist's reconstruction of these close human relatives, who seem to have disappeared from Europe some 50 thousand years ago. The general consensus is that Neandertals were brutish and went extinct when overtaken by modern humans, but that idea is undergoing ongoing revision as we learn more about these interesting members of the genus Homo.
    ::看看图像中的尼安德特人。这幅画是艺术家对这些近亲的重建,他们似乎在5万年前从欧洲消失。 普遍的共识是尼安德特人是野蛮的,在被现代人类取代时灭绝了,但是,随着我们更多地了解这些有趣的同族成员的情况,这一想法正在不断得到修改。

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    Neandertals were stocky and barrel-chested, but DNA evidence shows that they mated with modern humans thousands of years ago.
    ::尼安德特人长着袜子和桶子 但DNA证据表明 他们和现代人类交配 几千年前

    Several years ago, scientists were able to extract DNA from fossilized of Neandertals (see photo ). When the Neandertal DNA was compared to  modern human DNA, researchers discovered similarities between them, which suggests that modern humans mated with Neandertals. Some experts now think that Neandertals didn’t go extinct, but were simply incorporated into the much larger of Homo sapiens . 
    ::几年前,科学家得以从尼安德特人化石化化的尼安德特人身上提取DNA(见照片 ) 。 当尼安德特人DNA与现代人类DNA相比时,研究人员发现了它们之间的相似之处,这表明现代人类与尼安德特人交配。 如今,一些专家认为尼安德特人并没有灭绝,而只是融入了更大的智人之中。

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    A scientist works to extract DNA from a fossilized Neandertal bone.
    ::科学家从一个化石化的尼安德特骨骼中提取DNA

    New research published in Science  early in 2016 shows that our inherited Neandertal DNA may be more than just an interesting curiosity or useful evidence of our evolutionary past. These bits of DNA may actually be affecting our modern health. In the research reported in Science , scientists looked for Neandertal DNA sequences in the DNA from an electronic data base compiled from health records of almost 30 thousand modern American adults. The scientists found that certain segments of Neandertal DNA are especially common in people who have particular medical conditions, such as depression and increased amounts of clotting. Other bits of Neandertal DNA seem to  boost the immune response to certain parasites and other .
    ::2016年初在Science上发表的新研究表明,我们继承的NeandertalDNA可能不仅仅是一个有趣的好奇心或我们进化历史的有用证据。这些DNA部分实际上可能正在影响我们的现代健康。在科学研究中,科学家们从一个电子数据库中寻找DNA中的NeandertalDNA序列,该数据库来自近30 000名现代美国成年人的健康记录。科学家们发现,NeandertalDNA的某些部分在有特殊医疗条件的人中特别常见,如抑郁症和凝血量增加。其他的NeandertalDNA部分似乎刺激了对某些寄生虫和其他寄生虫的免疫反应。

    Most of the Neandertal DNA segments that have persisted in  our modern gene pool were probably beneficial in prehistoric times. Now, however, they may increase the risk of disease, because our lifestyles and environments have changed so much since then. For example, an increase in blood clotting would have helped prevent life-threatening bleeding from injuries or childbirth in the past, but today it may increase the risk of blood clots and strokes in older people with sedentary lifestyles. Even immune-boosting bits of Neandertal DNA  may now do more harm than good for Americans who live in environments where there are far fewer parasites. They may make our immune systems overactive and cause and autoimmune disorders.
    ::在我们现代基因库中持续存在的大部分尼安德特DNA部分在史前时期可能是有益的。 但是,现在,它们可能会增加疾病风险,因为我们的生活方式和环境从那时以来发生了巨大变化。 比如,血液凝血会有助于防止过去伤害或分娩造成的危及生命的出血,但今天,它可能会增加老年人以定居生活方式出现血块和中风的风险。 即使是免疫振动的尼安德特DNA部分现在也可能对生活在寄生虫少得多的环境中的美国人造成比好事更多的伤害。 它们可能使我们的免疫系统过度活跃,造成疾病和自发免疫紊乱。

    Summary
    ::摘要

    • Nucleic acids are the class of biochemical compounds that includes DNA and RNA. These molecules are built of small monomers called nucleotides, which bind together in long chains to form polynucleotides. DNA consists of two polynucleotides, and RNA consists of one polynucleotide.
      ::核糖核酸是包括DNA和RNA在内的生物化学化合物的类别,这些分子由称为核酸的小型单体组成,这些单体由长链结合形成多核酸。 DNA由两种多核酸组成,而核酸由一种多核酸组成。
    • Each nucleotide consists of a sugar molecule, phosphate group, and nitrogen base. Sugars and phosphate groups of adjacent nucleotides bind together to form the "backbone" of the polynucleotide. Nitrogen bases jut out to the side of the sugar-phosphate backbone. Bonds between complementary bases hold together the two polynucleotide chains of DNA and cause it to take on its characteristic double helix shape.
      ::每颗核糖酸由糖分子、磷酸类和氮基组成。糖和磷酸类相邻的核糖类和核酸类结合在一起形成聚核酸的“背骨 ” 。 氮基在糖-磷酸基柱的侧面起伏。 互补基点之间的键将两个多核酸类DNA链合在一起,并导致它以其特有的双螺旋形状形成。
    • DNA makes up genes, and the sequence of nitrogen bases in DNA makes up the genetic code for the synthesis of proteins. RNA helps synthesize proteins in cells. The genetic code in DNA is also passed from parents to offspring during reproduction, which explains  how inherited characteristics are passed from one generation to the next.
      ::DNA构成基因,而DNA中的氮基序列构成蛋白质合成的遗传代码。 RNA帮助细胞中合成蛋白质。DNA中的遗传代码在生殖过程中也从父母传给后代,这解释了遗传特征是如何一代传给下一代的。

    Review
    ::回顾

    1. What are nucleic acids?
    ::1. 什么是核酸?

    2. How does RNA differ structurally from DNA?
    ::2. RNA与DNA在结构上有何不同?

    3. Describe a nucleotide. Explain how nucleotides bind together to form a polynucleotide.
    ::3. 描述核分裂物,解释核分裂物是如何结合成一种多核分裂物的。

    4. What role do nitrogen bases in nucleotides play in the structure and function of DNA?
    ::4. 核糖核酸中的氮基在DNA的结构和功能中起什么作用?

    5. What is a function  of RNA?
    ::5. RNA的功能是什么?

    6. U sing what you learned in this article about nucleic acids, e xplain why Mark and Scott Kelly look so similar.
    ::6. 利用你在这篇文章中学到的有关核酸的知识,解释为什么马克和斯科特·凯利看起来如此相似。

    7. True or False:  A, C, G, and T represent the bases in RNA.
    ::7. 真实或假:A、C、G和T代表RNA的基地。

    8. True or False:  The two polynucleotide chains of RNA twist into a double helix shape.
    ::8. 真实或假:RNA的两个圆核酸链条扭曲成双螺旋形。

    9. True or False:  Cytosine always binds to guanine in DNA.
    ::9. 真实或假:Cytosine总是与DNA中的guanine捆绑在一起。

    10. If part of a chain of DNA has the sequence of bases ATTG, what is the corresponding sequence of bases that it binds to on the other chain?
    ::10. 如果DNA链的一部分有ATTG基地的顺序,那么它与其他链条相连的相应的基准顺序是什么?

    11. Arrange the following in order from the smallest to the largest level of organization:
    ::11. 按组织级别从最小组织级别到最大组织级别排列如下:

    DNA; nucleotide; polynucleotide
    ::DNA; 核酸; 核酸; 聚核酸

     

    12. As part of the DNA replication process, the two polynucleotide chains are separated from each other, but each individual chain remains intact. Which bonds are broken in this process?
    ::12. 作为DNA复制过程的一部分,两条多核酸链条相互分离,但每一条链条都完好无损,在这一过程中打破了哪些联系?

    a. bonds between adjacent sugars and phosphate groups
    ::a. 相邻糖类和磷酸盐类之间的债券

    b. bonds within nucleotides
    ::b. 核糖化物内的债券

    c. bonds between complementary bases
    ::c. 互补基础之间的债券

    d. bonds between adenine and guanine
    ::d. 和之间的债券

     

    13. Adenine, guanine, cytosine, and thymine are:
    ::13. Adenine、guanine、cytosine和甲状腺:

    a. nucleotides
    ::a. 核核糖化物

    b. nitrogen bases
    ::b. 氮基

    c. sugars in DNA and RNA
    ::c. DNA和RNA中的糖

    d. phosphate groups
    ::d. 磷酸酯类

    14. Some diseases and disorders are caused by genes. Explain why these genetic disorders can be passed down from parents to their children.
    ::14. 有些疾病和病症是由基因引起的,解释为什么这些遗传病可以由父母传给子女。

    Explore More
    ::探索更多

    In the  video below, Paul Rothemund discusses how to use computer   coding to create shapes using DNA. 
    ::Paul Rothemund在下面的影片中, 讨论如何使用电脑编码来利用DNA建立形状。


    Watch the video below to learn about the similarities between Neandertal and modern human  genetics.  
    ::看下面的录像 了解尼安德特人和现代人类基因的相似之处