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  • 变异

    A cartoon superhero in a blue and red costume with a cape, posing proudly.

    Would a mutation make you a superhero?
    ::突变会让你成为超级英雄吗?

    In the comic books, a mutation can give a person superpowers. Do you think this really happens? In real life, a mutation can be beneficial, or it can harm an organism . For example, beneficial mutations lead to evolution, and harmful mutations can lead to diseases like . A mutation, however, is not going to turn you into a superhero!
    ::在漫画书中,突变可以给一个人带来超能力。你认为这真的会发生吗?在现实生活中,突变可以带来好处,也可以伤害一个生物体。例如,有益的突变会导致进化,而有害的突变可以导致类似疾病。但是,突变不会把你变成超级英雄!

    Mutations
    ::变异

    The process of DNA replication is not always 100% accurate. Sometimes the wrong base is inserted in the new strand of . This wrong base could become permanent. A permanent change in the sequence of DNA is known as a mutation . Small changes in the DNA sequence are usually point mutations , which is a change in a single nucleotide . Once DNA has a mutation, that mutation will be copied each time the DNA replicates. After , each resulting cell will carry the mutation.
    ::DNA复制过程并不总是100%准确的。 有时错误的基点会插入到新的一系列中。 这种错误的基点可能会成为永久的。 DNA序列的永久性变化被称为突变。 DNA序列的微小变化通常是点变异, 也就是单核核酸的变异。 一旦DNA发生突变, 每当DNA复制时, 变异就会被复制。 之后, 每个生成的细胞都会随变异而出现 。

    A mutation may have no effect. However, sometimes a mutation can cause a protein to be made incorrectly. A defect in the protein can affect how well the protein works, or whether it works at all. Usually the loss of a protein function is detrimental to the organism.
    ::突变可能没有效果。 然而,有时突变可能导致蛋白质的生成错误。 蛋白质的缺陷会影响蛋白质的功能,或者说它是否有效。 蛋白质功能的丧失通常会损害生物体。

    In rare circumstances, though, the mutation can be beneficial. Mutations are a mechanism for how species evolve. For example, suppose a mutation in an animal’s DNA causes the loss of an enzyme that makes a dark pigment in the animal’s skin. If the of animals has moved to a light colored environment, the animals with the mutant gene would have a lighter skin color and be better camouflaged. So in this case, the mutation is beneficial.
    ::但是,在极少数情况下,突变可能是有益的。 突变是物种如何演变的一种机制。 比如,假设动物的DNA突变会导致导致动物皮肤染色变暗的酶消失。 如果动物迁移到浅色环境,则带有变种基因的动物将拥有较轻的肤色,并被更好的伪装。 因此,在这种情况下,突变是有益的。

    Point Mutations
    ::点变数

    If a single base is deleted (called a deletion, which is also a point mutation), there can be huge effects on the organism, because this may cause a frameshift mutation . Remember that the bases in the mRNA are read in groups of three by the tRNA. If the reading frame is off by even one base, the resulting sequence will consist of an entirely different set of codons .
    ::如果删除单一基数( 称为删除, 也就是点变异) , 有机体可能会受到巨大影响, 因为这可能导致框架变异 。 记住 mRNA 中的基数由 tRNA 以三为一组。 如果读数框架连一个基数都断开, 由此产生的序列将由完全不同的一套codon 组成 。

    The reading of an mRNA is like reading three-letter words of a sentence. Imagine the sentence: “The big dog ate the red cat.” If you take out the second letter from "big," the frame will be shifted so now it will read: “The bgd oga tet her edc at.” One single deletion makes the whole “sentence” impossible to read. A point mutation that adds a base (known as an insertion) would also result in a frameshift.
    ::读一个 mRNA 的文字就像读一个句子的三字母单词。 想象一下一句 :“ 大狗吃了红猫 ” 。 如果你从“ 大猫 ” ( big) 中取出第二封信, 框架就会被移开, 现在它会变成 :“ bgd oga tout her edc at ” 。 单删除一个字就使得整个“ 判决” 无法读懂。 添加一个基点(称为插入)的点突变也会导致一个框架变换 。

    Chromosomal Mutations
    ::染色变异

    Mutations may also occur in chromosomes ( Figure  ). These mutations are going to be fairly large mutations, possibly affecting many genes. Possible types of mutations in chromosomes include:
    ::染色体中也可能出现变异(图 ) 。 这些变异将会是相当大的变异, 可能影响许多基因。 染色体中可能发生的变异类型包括:

    1. Deletion: When a segment of DNA is lost, so there is a missing segment in the chromosome. These usually result in many genes missing from the chromosome.
      ::删除: 当一个DNA部分丢失时, 染色体中就有一个缺失的部分。 这通常会导致染色体中缺少许多基因。
    2. Duplication: When a segment of DNA is repeated, creating a longer chromosome. These usually result in multiple copies of genes in the chromosome.
      ::重复: 当重迭一个DNA段时, 会产生更长的染色体。 这通常会导致染色体中基因的多个复制件 。
    3. Inversion: When a segment of DNA is flipped and then reattached to the same chromosome.
      ::反向:当DNA的某一部分被翻转,然后重新连接到同一种染色体时。
    4. Insertion: When a segment of DNA from one chromosome is added to another, unrelated chromosome.
      ::插入:当一个染色体的DNA部分添加到另一个无关的染色体中时。
    5. Translocation: When two segments from different chromosomes change positions.
      ::变换位置:当来自不同染色体的两个区段改变位置时。
    Chromosome mutations: deletion, duplication, inversion, insertion, and translocation.
    Mutations can arise in DNA through deletion, duplication, inversion, insertion, and translocation within the chromosome.

    Causes of Mutations
    ::变异原因

    Many mutations are not caused by errors in replication . Mutations can happen spontaneously, and they can be caused by mutagens in the environment. Some chemicals, such as those found in tobacco smoke, can be mutagens. Sometimes mutagens can also cause cancer. Tobacco smoke, for example, is often linked to lung cancer .
    ::许多突变并非由复制错误引起的。 突变可能自发发生,也可能由环境中的诱变造成。 某些化学品,如烟草烟雾中发现的化学品,可能是诱变。 有时,诱变也可能引发癌症。 例如,烟草烟雾往往与肺癌有关。

    Summary
    ::摘要

    • A mutation is a permanent change in the sequence of bases in DNA.
      ::突变是DNA基数序列的永久性变化
    • Mutations occur in the DNA through deletion, duplication, inversion, insertion, and translocation within the chromosome.
      ::DNA中的变异通过染色体内的删除、重复、倒置、插入和移位发生。
    • Mutations can occur due to errors during DNA replication or by mutagens in the environment.
      ::由于DNA复制过程中的错误或环境中的诱变性,可能会发生变异。

    Explore More
    ::探索更多

    Use the resource below to answer the questions that follow.
    ::利用以下资源回答以下问题。

    • Types of Mutations - Understanding Evolution at 
      ::变异类型类型 -- -- 了解
    1. What is an example of a genetic disorder caused by a substitution mutation?
      ::替代突变引起的基因障碍的例子是什么?
    2. How can a substitution mutation change a protein?
      ::替代突变如何改变蛋白质?
    3. Explain a frameshift mutation.
      ::解释一个框架变异。
    4. What can cause a frameshift mutation?
      ::是什么导致框架变异?

    Review
    ::回顾

    1. Are mutations typically beneficial to the organism?
      ::突变通常有利于生物体吗?
    2. What can cause DNA to mutate?
      ::是什么导致DNA变异?
    3. What is a frameshift mutation?
      ::什么是轮廓变异?
    4. Describe two types of chromosomal mutations.
      ::描述两种染色体突变。