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  • 多诱变轨数

    A tall man and a shorter girl standing together, illustrating human height variation.

    Are all people either short or tall?
    ::所有人都是矮的还是高的?

    Unlike Mendel's peas, people do not all fall into two categories: short or tall. Most people, in fact, are somewhere in between. Obviously, Mendel's rules are too simple to explain the inheritance of human height.
    ::与门德尔豆不同的是,人们并不都分为两类:短或高。 事实上,大多数人都处在中间。 显然,门德尔的规则太简单,无法解释人身高的继承。

    Polygenic Traits
    ::多诱变轨数

    Another exception to Mendel’s rules is polygenic inheritance , which occurs when a trait is controlled by more than one gene . This means that each dominant allele "adds" to the expression of the next dominant allele.
    ::孟德尔规则的另一个例外是多基因继承,当一个特性受不止一个基因控制时,就会出现多基因继承。 这意味着,每个占支配地位的基因都“添加”到下一个占支配地位的变异物的表达中。

    Usually, traits are polygenic when there is wide variation in the trait. For example, humans can be many different sizes. Height is a polygenic trait, controlled by at least three genes with six alleles . If you are dominant for all of the alleles for height, then you will be very tall. There is also a wide range of skin color across people. Skin color is also a polygenic trait, as are hair and eye color.
    ::通常情况下, 当特性差异很大时, 特征是多致的。 例如, 人类可以是许多不同的大小。 高度是一种多致性特征, 由至少三个具有六个异长的基因控制的多致性特征。 如果您在高度上占所有异灵的主导地位, 那么你的身高会非常高 。 另外, 人的肤色也非常广泛。 皮肤颜色也是一种多致性特征, 头发和眼睛的颜色也是如此 。

    Polygenic inheritance often results in a bell shaped curve when you analyze the ( Figure ). That means that most people fall in the middle of the phenotypic range, such as average height, while very few people are at the extremes, such as very tall or very short. At one end of the curve will be individuals who are recessive for all the alleles (for example, aabbcc ); at the other end will be individuals who are dominant for all the alleles (for example, AABBCC ). Through the middle of the curve will be individuals who have a combination of dominant and recessive alleles (for example, AaBbCc or AaBBcc ).
    ::多生继承在分析(图 ) 时往往会导致钟形曲线。 这意味着大多数人跌落到峰值范围中间,比如平均高度,而很少有人处于极端状态,比如非常高或者非常短。 在曲线的一端,将是所有异类都处于休眠状态的个人(比如 aabbcc ) ; 在另一端,将是所有异类中占主导地位的个人(比如 AABBCC )。 通过曲线的中间部分,将有支配性和潜伏性异类(比如 AabbC 或 AABBcc ) 组合的个人(比如 AabC 或 AABBcc ) 。

    A bell-shaped curve representing the distribution of polygenic traits across a population.

    Polygenic traits tend to result in a distribution that resembles a bell-shaped curve, with few at the extremes and most in the middle. There may be 4 or 6 or more alleles involved in the phenotype. At the left extreme, individuals are completely dominant for all alleles, and at the right extreme, individuals are completely recessive for all alleles. Individuals in the middle have various combinations of recessive and dominant alleles.
    ::多致因特征往往导致类似于钟形曲线的分布,最极端和最中间的分布很少。 苯型可能涉及4或6个或更多的异灵。 在左端极端,所有异灵都完全以个人为主,在右端极端,所有异灵都完全处于休眠状态。 中端个人有各种休眠和占支配地位的异灵组合。

    Summary
    ::摘要

    • In polygenic inheritance, a trait is controlled by more than one gene.
      ::在多基因继承中,一个特性由不止一个基因控制。
    • Examples of polygenic inheritance include height or skin color.
      ::多源继承的例子包括身高或肤色。

    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。

    • Genetics and Eye Color at (1:49)
      ::遗传和眼色(1:49)
    1. Is eye color a trait controlled by a single gene as it is often taught in schools?
      ::眼色是否是学校经常教授的单一基因所控制的一种特征?
    2. Do you think skin color is a polygenic trait? Explain your reasoning, and be as specific as possible.
      ::你认为皮肤颜色是多元性特征吗?解释一下你的推理,尽可能具体。
    3. What is an albino? What kind of eyes would they definitely NOT have?
      ::白化病患者究竟是什么人?他们究竟没有什么样的眼睛呢?
    4. What is known about the melanin levels in people with blue eyes?
      ::蓝眼睛人体内的梅拉宁水平如何?

    Review
    ::回顾

    1. How does polygenic inheritance violate Mendel's rules?
      ::多基因继承如何违反门德尔的规则?
    2. Give examples of traits governed by polygenic inheritance.
      ::举例说明多基因继承所支配的特征。