Section outline

  • General

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  • 非男性继承人继承权

    What you will learn 
    ::你会学到什么

    • Complex patterns of inheritance other than those studied by
      ::继承的复杂模式,但研究的
    • The types of Non-Mendelian inheritance: codominance , incomplete dominance , multiple , and
      ::非Mendelian继承的种类:共同继承、不完全占支配地位、多重继承和
    • How environment affects the phenotype of an individual
      ::环境如何影响个人的苯型

    Close-up of a human eye with a greenish-blue iris and a dark pupil.

    Green, blue, brown, black, hazel, violet, or grey. What color are your eyes?
    ::绿色、蓝色、棕色、黑色、哈泽尔、紫色或灰色。

    Of course, human do not come in multi-color, but they do come in many colors. How do eyes come in so many colors? That brings us to complex inheritance patterns, known as non-Mendelian inheritance. Many times inheritance is more complicated than the simple patterns observed by Mendel.
    ::当然,人类不会以多色形式出现,但确实以多种颜色出现。眼睛如何以这么多颜色出现?这给我们带来了复杂的继承模式,被称为非曼德利人的继承。 许多情况下,继承比门德尔观察的简单模式复杂得多。

    Non-Mendelian Inheritance
    ::非男性继承人继承权

    The inheritance of characteristics is not always as simple as it is for the characteristics that Mendel studied in . Each characteristic Mendel investigated was controlled by one gene that had two possible alleles, one of which was completely dominant to the other. This resulted in just two possible phenotypes for each characteristic. Each characteristic Mendel studied was also controlled by a gene on a different (nonhomologous) . As a result, each characteristic was inherited independently of the other characteristics. Geneticists now know that inheritance is often more complex than this.
    ::所调查的曼德尔的每个特征都由一个基因所控制,其中一种基因具有两种可能的异长,一种完全主导另一个基因。这导致每种特性只有两种可能的苯型。所研究的每个特征也由一个不同(非异种)的基因所控制。结果,每一种特性都是独立于其他特性而继承的。现在,遗传学家们知道继承往往比这个复杂得多。

    A characteristic may be controlled by one gene with two alleles, but the two alleles may have a different relationship than the simple dominant- recessive relationship that you have read about so far. For example, the two alleles may have a codominant or incompletely dominant relationship. 
    ::一种特性可能由两种异形的基因来控制,但这两种异形可能与你迄今所读到的简单支配-衰退关系有不同的关系。 例如,这两种异系可能具有共占性或不完整的支配性关系。

    Codominance
    ::共居情况

    Codominance occurs when both alleles are expressed equally in the phenotype of the heterozygote , as shown in the Figure . The reddish-brown and white coat color in the example below has codominant alleles for reddish-brown coat color and white coat color in cows.
    ::如图所示,当两个异形体在异体zygote的苯型中均以等同的表达方式表示时,便会出现共占优势。下面的例子中的红褐色和白大衣颜色在奶牛中具有红褐色和白大衣颜色的共占优势。

    Punnett square showing codominance in cows with reddish-brown and white coat colors.
    Codominance of alleles for reddish-brown (R) and white coat color (W) in cows.

    Incomplete Dominance
    ::不完全占多数

    Incomplete dominance occurs when the phenotype of a heterozygote offspring is somewhere in between the phenotypes of both homozygous parents; a completely dominant allele does not occur. For example, when red snapdragons ( RR ) are crossed with white snapdragons ( WW ), the F 1 hybrids are all pink heterozygotes for flower color ( RW ). The pink color is an intermediate between the two parent colors. When two F 1 ( RW ) hybrids are crossed they will produce red, pink, and white flowers. The genotype of an organism with incomplete dominance can be determined from its phenotype. 
    ::当异体zygote后代的苯型在双同性古人父母的苯型之间某处时,就会出现完全的支配地位。例如,当红松鼠(RR)与白松鼠(WW)交错时,F1混合体就成了花色(RW)的粉色异体。粉色颜色是双父色之间的中间体。当两个F1(RW)混合体经过时,它们会产生红花、粉色花和白花。一个不完全占优势的有机体的基因类型可以从其苯型中确定。

    What are the missing genotypes in the cross below?
    ::下面十字架上缺少的基因型是什么?

    Multiple Alleles
    ::多个all

    Many genes have multiple (more than two) alleles. An example is ABO blood type in humans. There are three common alleles for the gene that controls this characteristic. The alleles I A and I B are dominant over i. A person who is homozygous recessive ii has type O . Homozygous dominant I A I A or heterozygous dominant I A i have type A blood, and homozygous dominant I B I B or heterozygous dominant I B i have type B blood. I A I B people have type AB blood, because the A and B alleles are codominant. Type A and type B parents can have a type AB child. Type A and type B parents can also have a child with Type O blood, if they are both heterozygous (I B i, I A i).
    ::许多基因有多种(超过两个)异形。 一个例子是人类中的ABO血型。 控制这一特征的基因有三个常见异源。 异源IA和IB占一等。 异源IA和IB占一等。 一个同源二的人有O型。 以IAIA或异源为主的IAIA为主的Hogygos有A型血。 以IBB或异源IB为主的同源各有B型血。 IAB人有AB型血,因为A类和B等异源是同源。 A类和B类父母可能有AB型孩子。 A类和B类父母也有O型血型孩子,如果他们都是异源(IBi、IAi)。

    • Type A blood: I A I A , I A i
      ::A型血:IAIA、IAi
    • Type B blood: I B I B , I B i
      ::B型血:IB IB、IB i
    • Type AB blood: I A I B
      ::AB型血:IAIB
    • Type O blood: ii
      ::O型血血:二

    What are the missing genotypes in the cross below?
    ::下面十字架上缺少的基因型是什么?

     

    Polygenic Trait s
    ::多诱变轨数

    Polygenic traits are controlled by more than one gene, and each gene may have two or more alleles. The genes may be on the same chromosome or on nonhomologous chromosomes.
    ::多基因特征由不止一个基因控制,每个基因可能有两种或两种以上的异系。 这些基因可能存在于同一个染色体或非血色染色体上。

    • If the genes are located close together on the same chromosome, they are likely to be inherited together. However, it is possible that they will be separated by crossing over during , in which case they may be inherited independently of one another.
      ::如果基因紧紧放在同一个染色体上,它们很可能被一起继承。 但是,它们有可能通过在(......)期间跨越而分离,在这种情况下,它们可能相互独立继承。
    • If the genes are on nonhomologous chromosomes, they may be recombined in various ways because of independent assortment .
      ::如果基因在非血色染色体上,它们可能因独立的异类而以不同方式重新组合。

    • Unlike traits that express as dominant or recessive phenotypes, polygenic traits usually appear as a range of phenotypes, as shown in the Figure .
      ::如图所示,与表现为主要或余生苯型的特征不同,多生性特征通常以一系列苯型形式出现。


      ::如图所示,与表现为主要或余生苯型的特征不同,多生性特征通常以一系列苯型形式出现。

    For these reasons, the inheritance of polygenic trait s is very complicated. Such characteristics may have many possible phenotypes. Skin color, eye color, and adult height are examples of polygenic  traits in humans. Do you have any idea how many phenotypes each characteristic has?
    ::基于这些原因,多基因特征的遗传非常复杂。 这些特征可能有多种可能的苯型。 皮肤颜色、眼睛颜色和成年身高是人类多基因特征的例子。 您知道每个特征有多少个苯型吗?

    Graph showing the frequency distribution of adult height in men and women.
    Human Adult Height. Like many other polygenic traits, adult height has a bell-shaped distribution.

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

    Genes play an important role in determining an organism’s characteristics. However, for many characteristics, the individual’s phenotype is influenced by other factors as well. Environmental factors, such as sunlight and food availability, can affect how genes are expressed in the phenotype of individuals. Here are just two examples:
    ::基因在确定生物体特征方面起着重要作用。 然而,对于许多特征来说,个人的苯型也受到其他因素的影响。 日光和食物供应等环境因素可以影响基因在个人苯型中的表达方式。 以下仅举两个例子:

    • Genes play an important part in determining our adult height. However, factors such as poor nutrition can prevent us from achieving our full genetic potential.
      ::基因在决定我们的成年身高方面起着重要作用,但是,营养不良等因素会妨碍我们充分实现我们的基因潜力。
    • Genes are a major determinant of human skin color. However, exposure to ultraviolet radiation can increase the amount of pigment in the skin and make it appear darker.
      ::基因是人类肤色的一个主要决定因素,但是,受紫外线辐射的照射可增加皮肤色素含量,使其看起来更暗。

     

     

    Check your understanding!
    ::检查你的理解!

     

     

    Summary
    ::摘要

    • Many characteristics have more complex inheritance patterns than those studied by Mendel. They are complicated by factors such as codominance, incomplete dominance, multiple alleles, and environmental influences.
      ::许多特征的继承模式比门德尔研究的更为复杂,其复杂性因下列因素而加剧:共占优势、不完全的支配地位、多重异性和环境影响。

    Review
    ::回顾

    1. A classmate tells you that a person can have type AO blood. Do you agree? Explain.
      ::同学说一个人可以有AO型血,你同意吗?
    2. Mendelian inheritance does not apply to the inheritance of alleles that result in incomplete dominance and codominance. Explain why this is so.
      ::门德利人遗产不适用于导致不完全占支配地位和共占支配地位的异种人的遗产,请解释为何如此。
    3. Describe the relationship between environment and phenotype.
      ::描述环境与苯型之间的关系。
    4. Mendel investigated stem length, or height, in pea plants. What if he had investigated human height instead? Why would his results have been harder to interpret?
      ::孟德尔调查了豆类植物的干干长度或身高。 如果他调查了人的身高呢? 为什么他的结果更难解释呢?