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  • 环境对遗传学的影响 -- -- 先进

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    What do these twins have in common?
    ::这些双胞胎有什么共同点?

    Almost all their . In fact, all their nuclear DNA. Some of their mitochondrial DNA may have slight variations. So that would mean that genetic studies involving twins can be potentially very rewarding.
    ::几乎所有的。事实上,他们所有的核DNA。有些它们的线粒体DNA可能略有不同。这意味着涉及双胞胎的遗传研究可能非常有益。

    Effects of Environment on Phenotype
    ::环境对基因型的影响

    Genes play an important part in influencing phenotype , but genes are not the only influence. Environmental conditions, such as temperature and availability of nutrients can affect phenotypes. For example, temperature affects coat color in Siamese cats.
    ::基因在影响苯型中起着重要作用,但基因并不是唯一的影响。 环境条件,如温度和营养物质供应可以影响苯型。 比如,温度会影响暹罗猫的外衣颜色。

    Effect of Environment on Phenotype.
    The dark “points” on this Siamese cat are caused by a gene that codes for a temperature-sensitive enzyme. The enzyme, which causes a darkening of the cat’s fur, is active only in the cooler parts of the body, such as the tail, feet, ears, and area around the nose.

    The pointed pattern is a form of partial albinism, which results from a in an that is involved in melanin production. The mutated enzyme is heat-sensitive; it fails to work at normal body temperatures. However, it is active in cooler areas of the skin. This results in dark coloration in the coolest parts of the cat's body, such as the lower limbs and the face, as shown in the Figure  . The cat’s face is cooled by the passage of air through the nose. Generally, adult Siamese cats living in warm climates have lighter coats than those in cooler climates.
    ::尖点模式是一种局部白化病, 其产自一种与梅兰宁生产有关的致癌物。 突变酶对热敏感, 无法在正常身体温度下工作 。 但是, 它在皮肤更冷的地方很活跃 。 这导致猫体最冷的部位, 如图中显示的下肢和脸部的暗色化 。 猫的表情被空气从鼻子中流过而冷却。 一般而言, 生活在温暖气候中的成年暹黄猫的外套比在较冷气候中的猫更轻。

    Height in humans is a complex phenotype influenced by many genes, but it is also influenced by nutrition. A person who eats a diet poor in nutrients will not grow as tall as they would have had they eaten a more nutritious diet.
    ::人类的体重是受许多基因影响的一种复杂的苯型,但也受营养的影响。 食用营养缺乏营养的饮食的人不会长得像吃更营养的饮食那样高。

    Environmental Trigger
    ::环境触发器

    Does everyone who smokes develop lung ? No, of course not. Is it possible to get lung cancer without smoking? Sadly, yes it is. That's not to say there is no relationship between the two: smoking is still the leading cause of lung cancer. But it does suggest that a person's genetic background has a role in this process. Apart from true single gene disorders, environmental factors, or environmental triggers , may determine the of disease in individuals genetically predisposed to a particular condition. Environmental triggers may include stress, physical and mental abuse, diet, exposure to toxins, , and radiation. Many cancers are thought to have an environmental component. It has been suggested that environmental factors play a role in autism as well. Asthma is obviously triggered under certain environmental conditions.
    ::吸烟者是否都发展了肺部? 当然不是。 不,当然不是。不吸烟者是否可能得了肺癌?不幸的是,是的。这不是说两者之间没有任何关系:吸烟仍然是肺癌的首要原因。但它确实表明一个人的基因背景在这个过程中可以发挥作用。除了真正的单一基因疾病、环境因素或环境触发因素之外,在遗传上容易发生某种特定情况的个体中,环境触发因素可能决定疾病。环境触发因素可能包括压力、身体和精神虐待、饮食、接触毒素和辐射。许多癌症被认为具有环境成分。人们认为环境因素在自闭症中也有作用。在某些环境条件下,阿斯马显然会引发。

    Twin Studies
    ::双生研究

    The classical twin design compares the similarity of identical and fraternal twins.
    ::古典双胞胎设计比较了相同和兄弟双胞胎的相似性。

    Scientists often study the effects of environment on phenotype by studying identical twins. Identical twins have the same genes, so phenotypic differences between twins often have an environmental cause. Twin studies help understand the relative importance of environmental and genetic influences on individual traits and behaviors. Twins are a valuable source of information concerning the relationship between genes and environment. As monozygotic twins (identical) share their nuclear DNA, their polymorphisms , the nucleotide differences that make their DNA unique, are common to the two individuals. This means that any phenotypic variation, such as in height, intelligence, or any other measurable trait, is due to the environment. What is different about the experiences of the twins? What unique experiences might one twin have that the other twin did not have? By comparing phenotypes of hundreds of twins, researchers can understand the roles of genetics , shared environment and unique experiences in the formation and development of specific traits.
    ::科学家常常通过研究同父双胞胎来研究环境对同父体的影响。同父双胞胎有着相同的基因,因此双胞胎之间的个性差异往往有环境原因。双胞胎研究有助于理解环境和遗传影响对个体特性和行为的相对重要性。双胞胎是有关基因和环境之间关系的宝贵信息来源。单子双胞胎(同父双胞胎)分享其核DNA,它们的多形态、使自己的DNA独一无二的核子酸差异对这两个人来说是常见的。这意味着任何个性差异,例如身高、智力或任何其他可测量的特性,都是由环境造成的。双胞胎的经历有什么不同?一个独特的经验可能是双胞胎所没有的?通过比较成双胞胎的个性类型,研究人员可以理解基因的作用、共同的环境以及特定特性形成和发展的独特经验。

    Dizygotic twins (fraternal or non-identical) share only about half of their polymorphisms. These twins are helpful to study as they tend to share many aspects of their environment. As they are born in the same place, usually within a few minutes of each other, they share many environmental conditions. They had the same in utero environment, they usually have a similar or the same parenting style during their childhood , and a similar or the same education. Similarities during childhood usually occur with wealth, culture, and their community.
    ::双胞胎(双胞胎或异性双胞胎)只占其多形态的大约一半,这些双胞胎有助于学习,因为他们往往分享环境的许多方面,因为他们出生在同一个地方,通常在几分钟之内,他们共同居住许多环境条件,在子宫环境中,他们通常在童年有相似或相同的养育方式,并有类似或相同的教育,童年的类似情况通常与财富、文化和社区相同。

    Modern twin studies have shown that almost all human traits are at least partly influenced by genetic differences. Some characteristics, such as height, show a strong genetic influence, while other characteristics have an intermediate level of genetic influence, such as with intelligence. Some characteristics have a much more complex genetic relationship, with evidence for different genes affecting different aspects of the trait. Autism, with its wide spectrum of severity, is such an example.
    ::现代的双重研究表明,几乎所有人类特征都至少部分受到遗传差异的影响。 一些特征,如身高,都表现出很强的遗传影响,而其他特征则具有中等遗传影响,如智力。 有些特征具有复杂得多的遗传关系,有证据表明不同基因影响特征的不同方面。 自闭症及其广泛严重性就是一个例子。

    Summary
    ::摘要

    • An organism’s phenotype can be influenced by environmental conditions.
      ::生物体的苯型可能受环境条件的影响。
    • Environmental triggers play a role in the development of disease in individuals genetically predisposed to that disease.
      ::环境触发因素在遗传上容易染上该疾病的个人的疾病发育中发挥作用。
    • Twin studies help scientists understand the relative importance of environmental and genetic influences on individual traits and behaviors.
      ::双胞胎研究有助于科学家了解环境和遗传影响对个人特性和行为的相对重要性。

    Review
    ::回顾

    1. Outline the relationship between environment and phenotype.
      ::概述环境与苯型之间的关系。
    2. What is an environmental trigger? Give an example.
      ::环境触发因素是什么?举个例子。
    3. What do twin studies provide?
      ::双胞胎研究能提供什么?
    4. What is the difference between monozygotic twins and dizygotic twins?
      ::双胞胎和双胞胎有什么区别?