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  • Genes 和 Alleles - 高级

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    Jeans vs. Genes. What's the difference?
    ::Jeans和Genes有什么区别?

    Plenty. One you have for life, the other just lasts a few years. One is the basis for the passing of traits from one generation to the next. Some jeans you change frequently. But what happens when you change a gene's frequency? Essentially, evolution is a change in gene frequencies within a .
    ::有很多。 一个你的生命,另一个只持续几年。 一个是基因从一代传到下一代的基础。 一些你经常改变的牛仔裤。 但是,当你改变基因频率时会发生什么? 从根本上说,进化是基因频率在某代的改变。

    Population Genetics
    ::人口基因遗传学

    If you have ever taken something apart to find out how it works, you will understand post-Darwinian biologists’ delight in exploring how evolution actually works. gave us the keys to unlocking this mystery by describing and common ancestry as scientific explanations for the similarities and differences among the millions of Earth’s – living and extinct. However, his theory depended on the ideas that traits could vary, and that variations were heritable – and even Darwin was puzzled as to how this might work. Another biological giant, Gregor , was a contemporary of Darwin’s, but his now-famous work with pea plant inheritance was not widely known or appreciated until after both scientists had died. During the 20th century, “re-discovery” of Mendel’s work stimulated extensive research in genetics , and the identification of as the universal genetic material of life, brought “heritable variation” into sharp focus. A branch of the new field of Population Biology finally combined what Mendel and Darwin had begun separately - the exploration of and the evolution of populations.
    ::如果你曾经拿了一些不同的东西来找出它是如何运作的,你会理解后达尔文生物学家在探索进化如何实际运作时的喜悦。 通过描述和共同的祖先来解释数以百万计的地球 — — 生存和灭绝 — — 之间的异同的科学解释,给我们打开这个神秘的钥匙。 但是,他的理论取决于特征可能不同的观点,而差异是遗传性的 — — 甚至达尔文也对此如何运作感到困惑。 另一个生物巨人Gregor(Gregor ) , 是达尔文的当代人,但他现在闻名的豆子植物继承工作直到两位科学家去世后才被广泛认识或赞赏。 在20世纪,门德尔作品的“重新发现”刺激了对基因学的广泛研究,并将“遗传变异性”确认为生命的通用遗传材料,因此引起了敏锐的焦点。 人口生物学新领域的一个分支最终将Mendel和达尔文开始的事物合并在一起 — — 人口探索和演变。

    You have studied genetics, DNA, and Darwinian evolutionary theory in previous chapters. You have had the opportunity to learn far more about biology than either Darwin or Mendel could imagine. You are prepared, then, to join biologists in exploring how evolution works. You know that biologists have massive amounts of evidence that natural selection and evolution happen. This chapter will explore what we know about how molecules, genes, and populations change – with the ultimate goal of understanding how the “Origin of Species” produced the vast diversity of life on Earth.
    ::你曾在前几章中研究过遗传学、DNA和达尔文进化理论。你有机会了解的生物学比达尔文或门德尔想象的要多得多。然后,你准备与生物学家一起探索进化的原理。 你知道生物学家有大量的证据证明自然选择和进化会发生。 本章将探讨我们所知道的分子、基因和人口如何变化 — — 最终目的是了解“物种的奥里金”如何产生地球上巨大的生命多样性。

    Genes and Alleles
    ::Genes 和 Alleles 基因和 Alleles 基因

    As you’ve learned, each of an organism contains all the information needed to build the entire organism in the DNA of its ( Figure ). A gene is a segment of DNA which has the information to code for a (or molecule) ( Figure ). For many genes, the protein product controls or at least contributes to a particular trait. For example, are proteins which are important in the controlling many cellular processes.
    ::正如你所知道的,每个生物体都包含在其DNA中构建整个生物所需的全部信息(图 ) 。 基因是DNA的一个部分,其信息可以编码一个(或分子 ) ( 图 ) 。 对于许多基因来说,蛋白质产品控制或至少有助于特定特性。 比如,蛋白质在控制许多细胞过程中很重要。

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    The source of variation required for natural selection is not traits or characters, as Darwin predicted, but the underlying genes, which were not discovered until Mendel’s work became known. Genes are segments of DNA located at a particular place on a chromosome. The gene’s sequence of bases codes for a protein - often an enzyme that catalyzes a particular chemical reaction in the cell. The chemical reaction determines or contributes to a physical trait or behavior.
    ::自然选择所需的变异来源不是达尔文所预测的特征或字符,而是根基基因,这些基因直到门德尔的工作被发现后才被发现。基因是DNA的一部分,位于染色体上的某个特定地方。基因的蛋白质基底代码序列 — — 通常是催化细胞中特定化学反应的酶。化学反应决定或促成了物理特征或行为。

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    A gene is a segment of DNA which codes for a protein. Proteins, in turn, determine traits. Changes in genes (mutations) cause changes in proteins, which in turn produce variation in traits.
    ::基因是DNA的一部分,它编码为蛋白质。 蛋白质反过来决定特性。 基因的变化(变异)导致蛋白质的变化,反过来又产生特性的变化。

    For example, the gene for the enzyme tyrosinase controls the chemical reaction which makes melanin , a brown-black pigment which colors the skin and hair of many , including humans. The gene is the “recipe” for tyrosinase; tyrosinase is the protein, and the trait is coloring of the skin or fur. The rabbit in  Figure has brown fur because its DNA contains a gene for tyrosinase.
    ::例如,酶抗抑郁酶的基因控制了化学反应,这种反应使美兰素成为美兰素,一种褐色黑色色色色,染色着包括人类在内的许多人的皮肤和头发。这个基因是抗抑郁素的“Recipe”;抗抑郁素是蛋白质,其特征是皮肤或毛皮的颜色。图中的兔子有棕色毛,因为它的DNA含有抗抑郁素的基因。

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    Most wild rabbits have brown fur because their DNA contains a gene which codes for tyrosinase – an enzyme which makes the pigment melanin.
    ::大部分野兔都有棕色毛皮, 因为他们的DNA含有一种抗抑郁酶编码的基因,

    Genes often have different forms – slightly different nucleotide sequences – known as alleles . In some rabbits, an alternative form of the gene for fur color makes non-functional tyrosinase. A change in the sequence of As, Ts, Cs, and Gs changes the sequence of amino acids in the protein and alters or destroys its activity. This allele is recessive and can cause lack of pigment – an albino rabbit ( Figure ). We will refer to the dominant gene for brown fur as B and the recessive gene for albinism as b.
    ::基因往往有不同的形式 — — 略微不同的核糖酸序列 — — 被称为“阿列斯 ” 。 在一些兔子中,毛皮色基因的替代形式导致不起作用的抗抑郁症。 As、Ts、Cs和Gs的序列变化改变了蛋白质中的氨基酸序列,并改变或摧毁了它的活动。 蛋白质是休眠的,可以导致缺乏色素 — — 白化兔子(Figure ) 。 我们将将棕色皮的主导基因称为 B , 白化病的休眠基因称为 b 。

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    If a rabbit receives two copies of the mutant allele for tyrosinase, it will lack pigment altogether – a condition known as albinism. Although these rabbits are obviously domesticated, mutations leading to albinism do occasionally occur in wild populations.
    ::如果兔子收到两本变异异异异异异异异体抗抑郁症,它就会完全缺乏色素 — — 一种被称为白化病的条件。 尽管这些兔子显然是被驯化的,但导致白化病的突变在野生人口中却偶尔发生。

    Recall that Mendel showed that humans and rabbits have two copies of each gene, or "heritable unit" – one from each of our parents. The two alleles we receive make up our genotype . For simple Mendelian traits, our genotype determines our physical appearance, or phenotype , for that trait. A rabbit having two copies of the mutant, recessive gene cannot make tyrosinase – or melanin; its genotype is bb, and its phenotype is albino. A rabbit having either one or two copies of the gene for tyrosinase makes melanin; its genotype is either Bb or BB, and in either case, because B is dominant, its phenotype is brown. Brown rabbits which have different alleles (genotype Bb ) are heterozygous , and brown rabbits with identical alleles ( BB ) are homozygous. Albino rabbits with identical recessive alleles ( bb ) are also homozygous.
    ::孟德尔(Mendel)指出,人类和兔子拥有每个基因的两份副本,即“可基因单位 ” — —每个父母各一份。我们得到的两个异名类组成了我们的基因型。对于简单的门德尔特质,我们的基因型决定了我们的外观,或者说这种特质的苯型。一个具有两种变异基因的兔子,休眠基因不能制造抗抑郁素 — — 或梅兰宁;它的基因型是bbb,它的苯型是albino。一个拥有一到两本苯基苯基的基因的兔子制造了梅兰尼;它的基因型是B或BB,在两种情况下,因为B占支配地位,其苯型是棕色。一个具有不同异名(geno型Bb)的棕色兔子是异名(异名Bb)的异名虫,而具有相同异名(BBB)的褐色兔子是同质。具有相同休止灵(bbbb)的阿比诺兔子也是同质。

    Keep in mind that the environment can influence the expression of a gene – its and to produce a protein. By preventing or promoting the expression of certain genes, the environment can cause variation in traits, but note that this influence is not at all goal-directed and does not result in heritable change. If you do not or fertilize your garden, the plants will be short and stunted, but their small size is not a heritable change. Let’s return to rabbits to see how this kind of variation happens at the level of genes and molecules.
    ::牢记环境可以影响基因的表达 — — 其并产生蛋白质。 通过防止或促进某些基因的表达,环境可以导致特性的变异,但注意到这种影响并非完全以目标为导向,也不会导致遗传性的变化。 如果你不这样做或施肥,植物就会短短和发育迟缓,但其体积小并不是一种遗传性的变化。 让我们回到兔子身上看看这种变异是如何在基因和分子水平上发生的。

    A third allele for rabbit fur coloration codes for a form of tyrosinase which is temperature-sensitive. At low temperatures, the enzyme makes melanin normally. Higher temperatures, however, denature the enzyme in the same way that cooking changes egg whites; at higher temperatures, the enzyme is misshapen and cannot make melanin. The rabbit in  Figure is homozygous for temperature-sensitive tyrosinase. The main part of its body, which has a higher temperature, is white because its tyrosinase does not work at high temperatures. The tips of the rabbit’s ears, nose, and feet, however, are black, because the enzyme can work at the slightly lower temperatures of these extremities. What do you think such a rabbit would look like if it developed in the ? The tropics?
    ::兔子毛皮色素的第三代色素代号为兔子毛皮色素的第三代代号,它具有温度敏感性。在低温下,酶通常会制造梅兰素。但是,较高的温度使酶变色化,就像烹饪改变蛋白一样;在高温下,酶会变色;在高温下,酶会变色,不能变梅兰素。图中的兔子是温度敏感性亚麻素的同质虫。其身体的主要部分是白色,因为它有较高的温度,因为它的麻黄素在高温下是行不通的。不过,兔子耳朵、鼻子和脚的尖头是黑色的,因为酶可以在这些极端的略低的温度上工作。你觉得这种兔子会像什么样子,如果它发展在热带地区呢?

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    Environment can influence the expression of a gene. California rabbits are bred for a temperature-sensitive allele of the pigment-producing enzyme tyrosinase. Cooler extremities produce melanin, but warmer body parts do not.
    ::环境可以影响基因的表达方式。 加利福尼亚的兔子生长于一种耐温的色素生成酶抗体外壳。 更冷却的体外可以产生梅林,但更温暖的人体部分却不会产生。

    In conclusion, heritable variations, which Darwin knew were necessary for natural selection, are determined by the variety of alleles, or different forms of genes, which build proteins. The environment may add to the variety of phenotypes by influencing , but the genes themselves remain unchanged. Only genes and their alleles can be sources of heritable variations in traits. 
    ::最后,达尔文所知道的遗传变异对于自然选择是必需的,由不同种类的异性或不同形式的基因决定,这些基因构成蛋白质。 环境可能通过影响而增加种类的苯型,但基因本身保持不变。 只有基因及其异性才能成为遗传特性变化的来源。

    Summary
    ::摘要

    • Population genetics studies populations at the level of genes and alleles in order to discover how evolution works.
      ::人口遗传学在基因和异象层次上对人口进行研究,以便发现进化是如何运作的。
    • Genes are segments of DNA which determine traits by coding for proteins that control chemical reactions (enzymes).
      ::基因是DNA的一部分,DNA通过控制化学反应(酶)的蛋白质编码确定特性。
    • Many genes have several different forms known as alleles.
      ::许多基因有几种不同的形式 叫做异形
    • Alleles are responsible for the variation in traits.
      ::异性通灵是特性变化的原因。
    • The environment can affect the expression of some genes, but variations induced by the environment are not heritable (unless environmental factors mutate DNA).
      ::环境可能影响某些基因的表达,但环境引起的变化是不可遗传的(除非环境因素改变DNA)。

    Review
    ::回顾

    1. Describe the relationship between genes and traits.
      ::描述基因和特性之间的关系。
    2. Explain the goal of population genetics.
      ::解释人口遗传学的目标。
    3. Differentiate between genes and alleles.
      ::基因和蛋白质之间的区别。
    4. Distinguish environmental effects on gene expression from allelic variations in genes.
      ::区分对基因表达方式的环境影响和基因的通灵变异。