章节大纲

  • lesson content

    Divide and Split
    ::除和拆分

    Can you guess what this colorful image represents? It shows a eukaryotic cell during the process of . In particular, the image shows the of the dividing. is located in the nucleus of most human cells. The nucleus divides before the cell itself splits in two, and before the nucleus divides, the cell’s DNA is replicated (or copied). There must be two copies of the DNA so that each daughter cell will have a complete copy of the genetic material from the parent cell . How is the replicated DNA sorted and separated so that each daughter cell gets a complete set of the genetic material? To answer that question, you first need to know more about DNA and the forms it takes.
    ::您能否猜到这幅多彩图像代表着什么? 它显示了一个在过程过程中的 Eukaryatic 单元格 。 特别是, 图像显示的分隔是位于大多数人类细胞的核心。 核心在细胞本身之前是分裂的, 在细胞本身分裂为两个, 在细胞核分裂之前, 细胞的DNA是复制的( 或复制的 ) 。 DNA必须有两个副本, 这样每个女儿细胞将拥有父细胞遗传材料的完整副本 。 复制的DNA是如何分类和分离的, 以便每个女儿细胞获得完整的基因材料 ? 要回答这个问题, 您首先需要了解更多DNA及其形式 。

    The Forms of DNA
    ::DNA的形式

    Except when a eukaryotic cell divides, its nuclear DNA exists as a grainy material called chromatin .  Only when a cell is about to divide and its DNA has replicated does DNA condense and coil into the familiar X-shaped form of a , like the one shown .  Most cells in the have two  pairs of 23 different chromosomes, for a total of 46 chromosomes.  Cells that have two pairs of chromosomes are called diploid .  Because DNA has already replicated when it coils into a chromosome, each chromosome actually consists of two identical structures called  sister chromatids. Sister chromatids are joined together at a region called a centromere .
    ::其核DNA作为称为染色体的质物质存在。只有当一个细胞即将分裂,而且其DNA已经复制时,它才会将DNA凝结并粘结成熟悉的X形形状的甲状腺,就像所显示的一样。大部分细胞有两对23种不同的染色体,共46种染色体。有两对染色体的细胞被称为diploid。由于DNA已经复制到一个染色体中,每个染色体实际上由两个相同的结构组成,叫做姐妹染色体。姐妹染色体在一个叫做centromere的区域被合并在一起。

    lesson content

    Chromosome. After DNA replicates, it forms chromosomes like the one shown here.
    ::染色体。DNA复制后, 它形成染色体 就像这里显示的染色体。

    Mitosis
    ::传染病

    The process in which the nucleus of a eukaryotic cell divides is called mitosis. During mitosis, the two sister chromatids that make up each chromosome separate from each other and move to opposite poles of the cell. This is shown in the figure . 
    ::eukaryatic 细胞分裂的核心被称作“ 分裂” 的过程。 在分裂过程中, 构成每个染色体的姐妹染色体, 并移动到细胞的对面极。 这在图中显示 。

    Mitosis is the phase of the eukaryotic cell cycle that occurs between DNA replication and the formation of two daughter cells. What happens during mitosis?
    ::微粒化是DNA复制和两个女儿细胞形成之间出现的自闭细胞循环的阶段。 在微粒化过程中会发生什么?

    Mitosis actually occurs in four phases. The phases are called prophase , metaphase , anaphase , and telophase . They are shown in the following figure and described in detail below.
    ::这些阶段称为前期阶段、后期阶段、前期阶段、后期阶段和中继阶段,如下图所示并详述。

    Mitosis in the Eukaryotic Cell Cycle. Mitosis is the multi-phase process in which the nucleus of a eukaryotic cell divides.
    ::在Eukaryod细胞循环中,消化是一种多阶段过程,在这种过程中,电子分裂细胞的核心是多阶段的。

    Prophase
    ::预 期

    The first and longest phase of mitosis is prophase . During prophase, chromatin condenses into chromosomes, and the nuclear envelope (the membrane surrounding the nucleus) breaks down. In cells, the centrioles near the nucleus begin to separate and move to opposite poles of the cell. Centrioles are small found only in eukaryotic cells. They help ensure that the new cells that form after cell division each contain a complete set of chromosomes. As the centrioles move apart, a spindle starts to form between them. The spindle, shown in the diagram , consists of fibers made of microtubules .
    ::分裂症的第一个和最长的阶段是预期阶段。 在预期阶段, 染色体会凝聚为染色体, 核包( 核核周围的膜) 破裂。 在细胞中, 核核附近的中子开始分离, 并移动到细胞的对极。 中子只在 eukarymodic 单元格中发现小。 它们有助于确保细胞分裂后形成的新细胞包含完整的染色体。 随着分子分离, 圆形开始形成。 图表中显示的螺旋是由微图组成的纤维组成 。

    Spindle. The spindle starts to form during prophase of mitosis. Kinetochores on the spindle attach to the centromeres of sister chromatids.
    ::螺旋体。 螺旋体开始形成于分裂的预期阶段。 脊椎体在与姐妹染色体的环形相连接的螺旋体上。

    Metaphase
    ::相相相 相 相 相 相 相 相 相 相 相 相 相

    During metaphase , spindle fibers attach to the centromere of each pair of sister chromatids. As you can see in the figure , the sister chromatids line up at the equator (or center) of the cell. The spindle fibers ensure that sister chromatids will separate and go to different daughter cells when the cell divides.
    ::在元阶段, 脊椎纤维附于每对姐妹染色体的丙红纤维中。 如图所示, 姐妹染色体排在细胞的赤道( 或中心) 。 脊椎纤维确保姐妹染色体分离, 当细胞分隔时, 进入不同的女儿细胞 。

    Chromosomes, consisting of sister chromatids, line up at the equator or middle of the cell during metaphase.
    ::由姐妹染色体组成的染色体染色体在元阶段时排在赤道或细胞中间。

    Anaphase
    ::相 相 相 相 相 相 相

    During anaphase , sister chromatids separate and the centromeres divide. The sister chromatids are pulled apart by the shortening of the spindle fibers. This is a little like reeling in a by shortening the fishing line. One sister chromatid moves to one pole of the cell, and the other sister chromatid moves to the opposite pole. At the end of anaphase, each pole of the cell has a complete set of chromosomes.
    ::相位时, 姐妹染色体分离, 中子分裂。 姊妹染色体因脊椎纤维缩短而分离。 这有点像在一条钓鱼线中转线。 一位姊妹染色体移动到细胞的一根柱子上, 另一位姊妹染色体移动到对面的柱子上。 在相位结束时, 细胞的每个极都有一整套染色体。

    Telophase
    ::电闪电

    During telophase , the chromosomes begin to uncoil and form chromatin. This prepares the genetic material for directing the metabolic activities of the new cells. The spindle also breaks down, and new nuclear envelopes form.
    ::在调频阶段,染色体开始脱凝和形成染色体,从而准备指导新细胞代谢活动的遗传材料。 脊椎也破裂,新的核封状也形成。

    Cytokinesis
    ::阴道

    Cytokinesis is the final stage of cell division. During cytokinesis, the cytoplasm splits in two and the cell divides, as shown  . In animal cells, the plasma membrane of the parent cell pinches inward along the cell’s equator until two daughter cells form.  Thus, the goal of mitosis and cytokinesis is now complete, because one parent cell has given  rise to two daughter cells. The daughter cells have the same chromosomes as the parent cell.
    ::Cytokinesis 是细胞分裂的最后阶段。 在细胞分裂期间, 细胞的细胞分裂为两个, 细胞分裂为两个, 细胞分裂为两个。 在动物细胞中, 母细胞的等离子膜会紧紧地沿着细胞赤道向内挤, 直到两个女儿细胞形成。 因此, 细胞分裂和细胞分裂的目标现在已经完成, 因为一个母细胞产生了两个女儿细胞。 女儿细胞的染色体与母细胞的染色体相同 。

    lesson content

    Cytokinesis is the final stage of eukaryotic cell division.
    ::Cytokinesis是Eukaryaty细胞分裂的最后阶段。

    Summary
    ::摘要

    • Until a eukaryotic cell divides, its nuclear DNA exists as a grainy material called chromatin. After DNA replicates and the cell is about to divide, the DNA condenses and coils into the X-shaped form of a chromosome. Each chromosome actually consists of two sister chromatids, which are joined together at a centromere.
      ::直到衣原体细胞分裂,其核DNA作为称为染色体的质状材料存在。在DNA复制和细胞即将分离后,DNA凝结和卷圈形成染色体的X形形式。每个染色体实际上由两个姐妹染色体组成,它们以纯色相组合在一起。
    • Mitosis is the process during which the nucleus of a eukaryotic cell divides. During this process, sister chromatids separate from each other and move to opposite poles of the cell. This happens in four phases: prophase, metaphase, anaphase, and telophase.
      ::软化是单体细胞核心分裂的过程。 在此过程中, 姐妹染色体彼此分离, 并移动到细胞的对面极。 这分为四个阶段: 预期、 元阶段、 元阶段和调频阶段 。
    • Cytokinesis is the final stage of cell division, during which the cytoplasm splits in two and two daughter cells form.
      ::Cytokinesis是细胞分裂的最后阶段,在细胞分裂期间,细胞托盘分解成两个和两个女儿细胞。

    Review
    ::回顾

    1. Describe the different forms that DNA takes before and during cell division in a eukaryotic cell.
    ::1. 描述DNA在单体细胞细胞分解之前和期间采取的不同形式。

    2. Identify the four phases of mitosis in an animal cell, and summarize what happens during each phase.
    ::2. 查明动物细胞中分裂症的四个阶段,并总结每个阶段发生的情况。

    3. Explain what happens during cytokinesis in an animal cell.
    ::3. 解释在动物细胞细胞细胞细胞化期间发生的情况。

    4. What are the main differences between mitosis and cytokinesis?
    ::4. 肾上腺素和细胞外科素的主要区别是什么?

    5. The familiar X-shaped chromosome represents:
    ::5. 熟悉的X形染色体代表:

    a. how DNA always looks in eukaryotic cells
    ::a. eukaryaty细胞中的DNA总是如何外观

    b. how DNA in eukaryotic cells looks once it is replicated and the cell is about to divide
    ::b. eukaryaty细胞中的DNA一旦被复制,而且细胞即将分裂,其外观如何?

    c. female sex chromosomes only
    ::c. 只有女性性别染色体

    d. how DNA appears immediately after cytokinesis
    ::d. 细胞基离子反应后DNA立即出现的情况

     

    6. Which of the following is not part of a chromosome in eukaryotic cells?
    ::6. 下列哪一种不是衣原体细胞染色体的一部分?

    a. centriole
    ::a. 中

    b. centromere
    ::b. 丙烯

    c. chromatid
    ::c. 染色体

    d. DNA
    ::d. DNA

     

    7. What do you think would happen if the sister chromatids of one of the chromosomes did not separate during mitosis?
    ::7. 如果一个染色体的姐妹染色体在分裂期间没有分离,你认为会发生什么情况?

     

    8. Put the following processes in order of when they occur during cell division, from first to last:
    ::8. 将以下过程按细胞分裂期间的先后顺序排列,从头到尾:

    separation of sister chromatids; DNA replication; cytokinesis; lining up of chromosomes in the center of the cell; condensation and coiling of DNA into a chromosome
    ::姐妹染色体分离;DNA复制;血清复制;细胞基尼西;细胞细胞中心染色体排列;DNA凝结并合为染色体

     

    9. Why do you think the nuclear envelope breaks down at the start of mitosis?
    ::9. 为什么你认为核弹封套在开始分裂时会崩溃?

     

    10. The fibers made of microtubules that attach to the centromeres during mitosis are called ____________.
    ::10. 由与中子硬化过程中的中子附着的微细胞构成的纤维称为。

     

    11. True or False:  Chromosomes begin to uncoil during anaphase.
    ::11. 真实或假:染色体在周期期间开始不凝固。

     

    12. True or False:  During cytokinesis in animal cells, sister chromatids line up along the equator of the cell.
    ::12. 真实或假的:在动物细胞细胞细胞中,姐妹染色体排在细胞赤道一带。

    13. True or False:  After mitosis, the result is typically two daughter cells with identical DNA to each other.
    ::13. 真实或假的:在分裂后,结果通常是两个女儿细胞,彼此具有相同的DNA。

    Explore More
    ::探索更多

    Watch the video below to visualize mitosis.   
    ::观看下面的视频 以直观地观察脑硬化。

      The animation below demonstrates how nondisjunction can occur.
    ::下面的动画展示了如何实现非互不相容。