章节大纲

  • 常规

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  • 染色体

    What you will learn
    ::你会学到什么

    • Chromosomes and their structure
      ::染色体及其结构
    • How genes are related to chromosomes
      ::基因与染色体的关系
    • The number of chromosomes in human
      ::人类染色体数量

    Chromosomes illustrating their shape and arrangement before cell division.

    How is it assured that every cell in your body has the same DNA?
    ::如何保证你身体里的每个细胞 都有相同的DNA?

    Chromosomes, like those shown here, must form prior to , to ensure that each daughter cell receives a complete set of genetic material . Essentially, each new cell receives half of each "X-shaped" chromosome.
    ::染色体和这里显示的染色体一样,必须在......之前形成,以确保每个女儿细胞都得到一整套遗传材料。 基本上,每个新细胞都得到每个“X形”染色体的一半。

    Chromosomes
    ::染色体

    In eukaryotic cells , the divides before the cell itself divides. The process in which the nucleus divides is called . Before mitosis occurs, a cell’s is replicated. This is necessary 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 understand how this happens, you need to know more about chromosomes.
    ::在 eukaryatic 单元格中, 细胞本身之前的分差会分裂。 核分法被称之为 。 在出现分裂之前, 细胞会被复制。 这很有必要, 以便每个女儿的细胞都能从母细胞中获取完整的遗传材料。 复制的DNA是如何分解和分离的, 以便每个女儿的细胞都能得到完整的遗传材料 ? 要了解这种情况, 您需要了解更多有关染色体的信息 。

    Chromosomes are coiled structures made of DNA and . Chromosomes are the form of the genetic material of a cell during cell division. It is this coiled structure that ensures the proper segregation of the chromosomes during cell division. During other phases of the , DNA is not coiled into chromosomes. Instead, it exists as a grainy material called chromatin .
    ::染色体是由DNA和染色体构成的结扎结构。染色体是细胞分裂期间细胞遗传物质的形式。正是这种结扎结构确保了细胞分裂期间染色体的适当隔离。在细胞分裂的其他阶段,DNA没有被结为染色体。相反,它是一种称为染色素的谷物材料。

    Chromatids and the Centromere
    ::染色体和中心

    DNA condenses and coils into the familiar X-shaped form of a chromosome only after it has replicated. Because DNA has already replicated, each chromosome actually consists of two identical copies. The two copies are called sister chromatids . They are attached to one another at a region called the centromere . 
    ::DNA在复制后才会凝结并凝结为一种熟悉的X形染色体。由于DNA已经复制,每个染色体实际上由两个相同的副本组成。两个副本被称为姐妹染色体。它们相互连接在一个叫做centromere的区域。

    Chromosomes and Genes
    ::染色体和基因

    The DNA of a chromosome is encoded with genetic instructions for making proteins. These instructions are organized into units called genes . Most genes contain the instructions for a single protein. There may be hundreds or even thousands of genes on a single chromosome.
    ::染色体的DNA被编码为用于制造蛋白质的遗传指令。 这些指令被组织成称为基因的单位。 大多数基因包含单一蛋白的指令。 单一染色体上可能有数百甚至数千个基因。

    Human Chromosomes
    ::人类染色体

    Human cells normally have two sets of chromosomes, one set inherited from each parent. There are 23 chromosomes in each set, for a total of 46 chromosomes per cell. Each chromosome in one set is matched by a chromosome of the same type in the other set, so there are actually 23 pairs of chromosomes per cell. Each pair consists of chromosomes of similar size and shape that also contain the same genes, but different (alternate forms of a gene). The chromosomes in a pair are known as homologous chromosomes .
    ::人类细胞通常有两组染色体,每组由父母继承一套。每组有23个染色体,每组共46个染色体。每组中,每组中每个染色体都配有同一类型的染色体,因此每组中实际上有23对染色体。每组中,每组中每组有23对染色体。每组由类似大小和形状的染色体组成,其中也包含相同的基因,但不同(一种基因的不同形式)。一组中的染色体被称为同质染色体。

     

     

     

    DID YOU KNOW?
    The number of chromosomes in an organism is not related to how big or complex the organism is. The largest number of chromosomes for an organism is present in a plant, Ophioglossum reticulatum , commonly known as the adder’s tongue .
     

    Summary
    ::摘要

    • Chromosomes are coiled structures made of DNA and proteins.
      ::染色体是由DNA和蛋白质组成的循环结构。
    • Chromosomes form after DNA replicates; prior to replication, DNA exists as chromatin.
      ::DNA复制后形成的染色体为染色体;在复制之前,DNA作为染色体存在。
    • Chromosomes contain genes, which code for proteins.
      ::染色体含有基因 蛋白质代码
    • Human cells normally have 46 chromosomes, made up of two sets of chromosomes, one set inherited from each parent.
      ::人类细胞通常有46种染色体,由两套染色体组成,一套是父母各继承的染色体。

    Review
    ::回顾

    1. What are chromosomes? When do they form?
      ::什么是染色体?
    2. Identify the chromatids and the centromere of a chromosome.
      ::识别染色体和染色体的中色素
    3. Explain how chromosomes are related to chromatin. Why are chromosomes important for mitosis?
      ::解释染色体与染色体的关系。 为什么染色体对分裂症很重要?
    4. How many chromosomes are in a normal human cell?
      ::正常的人体细胞里有多少染色体?