Section outline

  • Different traits in pea seeds.

    Round and green, round and yellow, wrinkled and green, or wrinkled and yellow?
    ::圆的、圆的、黄的、皱的、绿的、皱的、黄的呢?

    Can two traits be inherited together? Or are all traits inherited separately? asked these questions after his first round of . And the answer to the first question is Yes. And the answer to the second question is also Yes. And Mendel's work began to explain how this is so.
    ::两种特征是否可以一起继承? 还是所有特征都是分开继承的? 在他第一轮之后问了这些问题。第一个问题的答案是是肯定的。第二个问题的答案也是肯定的。门德尔的工作开始解释为什么如此。

    Mendel’s Second Experiment
    ::门德尔的第二次实验

    After Mendel's first set of experiments, Mendel wanted to see if the inheritance of characteristics were dependent, or were they independent events. Mendel asked if the segregation of the heritable factors (allele) for one characteristic (gene) had any effect of the segregation of the factors for another characteristic. For example, did the segregation of the flower color factors have any effect on the segregation of the seed shape factors? So Mendel performed crosses in which he followed the segregation of two genes . Mendel crossed that differed in two characteristics, such as seed color and shape. A dihybrid cross is a cross in which the inheritance of two characteristics are tracked at the same time. The offspring of such a cross are called dihybrids .
    ::在Mendel的第一组实验之后, Mendel 想要看看特性的继承是依附的,还是独立的事件。 Mendel 问一个特性( gene) 的可遗传因素( allele) 的分离是否对另一个特性( gene) 的可遗传因素( alle) 的分离有任何影响。 例如, 花朵颜色因素的分离是否对种子形状因素的隔离有任何影响? 所以 Mendel 进行了十字架, 他跟踪了两个基因的分离。 Mendel 跨越了十字架, 有两个特性不同, 比如种子颜色和形状。 双子十字是一个十字架, 同时跟踪两个特性的继承。 这种十字架的后代被称为二子。

    Once again Mendel began with a true-breeding P generation , but this time true-breeding for two characteristics. For example, he crossed pea plants that had yellow and round seeds with a plant that had green and wrinkled seeds. From Mendel's first experiments, yellow seed color is dominant to green seed color, and round seed shape is dominant to wrinkled. So for the F 1 generation, as before, the recessive traits disappeared, leaving Mendel with pea plants that had only round and yellow seeds. He then allowed the F 1 generation to self-pollinate , and examined the resulting F 2 generation. In the F 2 generation, the recessive traits reappeared, as did two novel combinations of traits: round green seeds, and wrinkled yellow seeds. From these results, Mendel concluded that characteristics were inherited independently of each other. That is the only way that the two new combinations of traits could have developed. From these findings, Mendel developed his second law , the Law of Independent Assortment .
    ::门德尔再次以真实的P一代开始, 但这次却是真实的P一代开始, 但有两个特点。 例如, 他跨过豆种, 有黄色的和圆的种子, 有绿色的和皱纹的种子。 从门德尔的第一次实验中, 黄色的种子颜色是绿色的种子颜色的主导, 圆的种子形状是皱纹的主导。 因此对F1的一代来说, 断裂的特性消失了, 留下只有圆的和黄色种子的豆类植物。 然后, 他允许F1的一代自我污染, 并检查由此产生的F2一代。 在F2的一代中, 断裂的特性重新出现, 两种新颖的特征组合: 圆绿色种子, 和皱纹的黄色种子。 从这些结果中, 门德尔得出结论, 特性是相互独立的。 这是两种新的特征组合能够发展的唯一方法。 从这些发现中, 门德尔发展了他的第二法律, 独立分类法。

    lesson content
    This chart represents Mendel's second set of experiments. It shows the outcome of a cross between plants that differ in seed color (yellow or green) and seed form (shown here with a smooth round appearance or wrinkled appearance). The letters R, r, Y, and y represent genes for the characteristics Mendel was studying. Mendel didn’t know about genes, however. Genes would not be discovered until several decades later. This experiment demonstrates that in the F2 generation, 9/16 were round yellow seeds, 3/16 were wrinkled yellow seeds, 3/16 were round green seeds, and 1/16 were wrinkled green seeds.
    Mendel's Dihybrid Cross
    seed possibilities P generation F 1 generation F 2 generation
    round & yellow X all 9
    round & green -- -- 3
    wrinkled & yellow -- -- 3
    wrinkled & green X none 1

    The Law of Independent Assortment
    ::独立等级法

    The Law of Independent Assortment , also known as or Mendel's Second Law, states that the inheritance of one trait will not affect the inheritance of another. Mendel concluded that different traits are inherited independently of each other, so that there is no relationship, for example, between seed color and seed shape. In modern terms, of each gene separate independently during gamete formation.
    ::《独立组别法》(又称《孟德尔第二法》)规定,一个特性的继承不会影响另一个特性的继承。 门德尔认为,不同的特性是相互独立继承的,因此种子颜色和种子形状之间没有关系。 从现代角度看,每个基因在基因形成期间独立分离。

    Mendel's Laws Rediscovered
    ::门德尔法律重新覆盖

    You might think that Mendel's discoveries would have made a big impact on science as soon as he made them. But you would be wrong. Why? Because Mendel's work was largely ignored. Mendel was far ahead of his time and working from a remote monastery. He had no reputation among the scientific community and limited previously published work.
    ::你可能会认为曼德尔的发现 会对科学产生巨大影响。但是你错了。为什么?因为曼德尔的工作基本上被忽视了。门德尔远超他的时间,在遥远的修道院工作。他在科学界没有名声,以前出版的作品也很有限。

    Mendel’s work, titled Experiments in Plant Hybridization , was published in 1866, and sent to prominent libraries in several countries, as well as 133 natural science associations. Mendel himself even sent carefully marked experiment kits to Karl von Nageli, the leading botanist of the day. The result - it was almost completely ignored. Von Nageli instead sent hawkweed seeds to Mendel, which he thought was a better plant for studying heredity . Unfortunately hawkweed reproduces asexually, resulting in genetically identical clones of the parent.
    ::孟德尔的作品《植物混合实验》于1866年出版,并被送往几个国家的著名图书馆以及133个自然科学协会。 门德尔本人甚至把精心标记的实验包送到当年主要植物学家卡尔·冯·纳吉利(Karl von Nageli ) 。 结果 — — 几乎完全被忽略了。 冯·纳吉利(Von Nageli)却把鹰毛种子送到门德尔(Mendel),他认为这才是学习遗传学的更好植物。 不幸的是,鹰毛猴繁殖了异性生殖,导致母体基因相同的克隆。

    Charles Darwin published his landmark book on evolution in 1869, not long after Mendel had discovered his laws. Unfortunately, Darwin knew nothing of Mendel's discoveries and didn’t understand heredity. This made his arguments about evolution less convincing to many people. This is an example of the importance of the scientific inquiry mindset elimination of bias.
    ::查尔斯·达尔文在1869年出版了他关于进化的具有里程碑意义的著作,在曼德尔发现自己的法律不久之后。 不幸的是,达尔文对门德尔的发现一无所知,也不理解异端。 这使得他关于进化的论点对许多人来说不那么令人信服。 这是科学调查消除偏见的重要性的一个例子。

    Even though he had repeated his studies using thousands of pea plants, and applied statistics to analyze his findings, Mendel's work was initially rejected as most biologists still believed in blending inheritance, and they did not understand his laws. It was not until after he died (January 6, 1884) that his work gained wide acceptance. By 1900, research into discontinuous inheritance - why do traits "disappear" in the F 1 generation? - led to independent duplication of Mendel's work by Hugo de Vries and Carl Correns, and then the rediscovery of Mendel's writings and laws. Soon afterwards, other biologists started to establish genetics , the study of heredity, as a science.
    ::尽管他重复了使用数千种豆子植物的研究,并运用了统计数据来分析他的调查结果,但Mendel的工作最初却遭到拒绝,因为大多数生物学家仍然相信混合继承,而且他们不理解他的法律。直到他去世之后(1884年1月6日),他的工作才获得广泛接受。到了1900年,对不连续继承的研究 — — 为何F1世代的特征“消失 ” ? — —导致Hugo de Vries和Carl Correns独立重复Mendel的工作,然后重新发现Mendel的著作和法律。 不久之后,其他生物学家开始将遗传学、遗传学研究作为科学进行。

    Linked Genes on Chromosomes
    ::染色体上的链接基因

    We now know that the only alleles that are inherited independently are ones that are located far apart on a or that are on different chromosomes. There are many genes that are close together on a chromosome, and are packaged into the gametes together. Genes that are inherited in this way are called linked genes . Linked genes tend to be inherited together because they are located on the same chromosome; that are located at the same locus . Genes located for apart on the same chromosome, at different loci , may be inherited separately due to a possible genetic recombination event during prophase I of . was first discovered by the British geneticists William Bateson and Reginald Punnett shortly after were rediscovered.
    ::我们现在知道,唯一独立继承的异系物是位于一个不同染色体上或不同染色体上的异系物。许多基因在染色体上紧密相连,并被包装在一起。以这种方式继承的基因被称为关联基因。连接的基因往往被共同继承,因为它们位于同一个染色体上;位于同一地点。同一染色体上的异系物,在不同地点,可能由于在前一阶段可能发生的基因重组事件而分别继承。英国遗传学家William Bateson 和 Reginald Punnett不久就发现了这些基因,这些基因被重新发现。

    Summary
    ::摘要

    • The law of independent assortment states that the inheritance of one trait will not affect the inheritance of another. That is, genes are inherited independently of each other.
      ::独立等级法规定,一个特性的继承不会影响另一个特性的继承,也就是说,基因是相互独立继承的。
    • Linked genes are genes that are close together on the same chromosome. Linked genes are inherited together.
      ::连接基因是紧密结合在同一染色体上的基因。 连接基因是一起遗传的。 连接基因是一起遗传的。 连接基因是一起遗传的。 连接基因是一起遗传的。

    Review
    ::回顾

    1. What is a dihybrid cross?
      ::半合金十字架是什么?
    2. Describe Mendel's second experiment.
      ::描述Mendel的第二次实验
    3. Summarize the law of independent assortment.
      ::概述独立的各类法律。
    4. Which genes are independently assorted and which aren't?
      ::哪些基因是独立的,哪些不是?