Section outline

  • General

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  • 人类染色体

    What you will learn
    ::你会学到什么

    • What are and how many chromosomes are present in human somatic
      ::人类体格中的染色体是什么以及有多少染色体
    • What are autosomes and sex chromosomes
      ::什么是异体和性染色体
    • How many genes are present in the
      ::有多少基因存在于这些基因中?

    Chromosomes, representing DNA bundles that carry genes in human cells.

    Coiled bundles of DNA and proteins, containing hundreds or thousands of genes. What are these things?
    ::堆肥的DNA和蛋白质包裹,含有数百或数千个基因。这些是什么?

    Chromosomes. These ensure that each cell receives the proper amount of during . And usually people have 46 of them, 23 from each parent.
    ::染色体。这些确保每个细胞在 . . . . . . 通常人们有46个细胞, 23个来自每个父母。

    Chromosomes and Genes
    ::染色体和基因

    Each has a characteristic number of chromosomes. Chromosomes are coiled structures made of DNA and called histones . Chromosomes are the form of the genetic material of a cell during cell division.
    ::染色体是由DNA和直方体组成的连接结构。染色体是细胞分裂期间细胞遗传物质的形式。

    The human species is characterized by 23 pairs of chromosomes.
    ::人类的特征是23对染色体。

    Autosomes
    ::自动

    Of the 23 pairs of human chromosomes, 22 pairs are autosomes (numbers 1–22 ) and the 23 rd pair consists of sex chromosomes, X and Y , hover over the terms to see these illustrated in the Figure . Autosomes are chromosomes that contain genes for characteristics that are unrelated to sex. These chromosomes are the same in males and females. The great majority of human genes are located on autosomes.
    ::在23对人类染色体中,22对是异体(编号1-22),23对由性染色体、X和Y组成,徘徊在图中所示的术语上,以查看这些术语。 异体是染色体,含有与性别无关的特征的基因。这些染色体在男性和女性中是相同的。绝大多数人类基因都位于异体上。

    Sex Chromosomes
    ::性染色体

    The remaining pair of human chromosomes consists of the sex chromosomes , X and Y. Females have two X chromosomes, and males have one X and one Y chromosome . In females, one of the X chromosomes in each cell is inactivated and known as a Barr body. This ensures that females, like males, have only one functioning copy of the X chromosome in each cell.
    ::其余的一对人类染色体由性染色体、X和Y组成。 女性有2个X染色体,男性有1个X和1个Y染色体。在女性中,每个细胞中的1个X染色体没有活性,被称为巴尔身体。这确保了女性与男性一样,每个细胞中只有1个X染色体的功能副本。

    As you can see from the Figures above, the X chromosome is much larger than the Y chromosome. The X chromosome has about 2,000 genes, whereas the Y chromosome has fewer than 100, none of which are essential to survival. (For comparison, the smallest autosome, chromosome 22, has over 500 genes.) Virtually all of the X chromosome genes are unrelated to sex. Only the Y chromosome contains genes that determine sex. A single Y chromosome gene, called SRY (which stands for sex-determining region Y gene), triggers an embryo to develop into a male. Without a Y chromosome, an individual develops into a female, so you can think of female as the default sex of the human species. Can you think of a reason why the Y chromosome is so much smaller than the X chromosome?
    ::从以上的数字中可以看到,X染色体比Y染色体大得多。X染色体有大约2,000个基因,而Y染色体有不到100个基因,而Y染色体没有生存所必需的任何基因。 (比较而言,最小的异体体,染色体22个,有500多个基因。 )几乎所有的X染色体基因都与性无关。只有Y染色体含有决定性别的基因。一个叫SRY的单一Y染色体基因(代表性别-确定区Y基因),触发胚胎发展成男性。没有Y染色体,一个人就会发展成女性,这样你就可以把女性视为人类物种的默认性别。你能想到为什么Y染色体比X染色体小得多吗?

    DID YOU KNOW?
    Bees, wasps, and ants do not have sex chromosomes. In these organisms , sex is determined by . Fertilized eggs develop into females, and unfertilized eggs hatch into males.
     

    Human Genes
    ::人类基因

    Humans have an estimated 20,000 to 22,000 genes. This may sound like a lot, but it really isn’t. Far simpler species have almost as many genes as humans. However, human cells use splicing and other processes to make multiple proteins from the instructions encoded in a single gene. Of the 3 billion base pairs in the human genome, only about 25 percent make up genes and their regulatory elements . The functions of many of the other base pairs are still unclear.
    ::人类的基因估计有20,000到22,000个。这听起来可能听起来像很多,但确实不是。 更简单的物种的基因几乎和人类一样多。 然而,人类细胞利用拼凑和其他过程从单基因编码的指示中制造多种蛋白质。 在人类基因组的30亿对基对中,只有25%左右组成基因及其调控要素。 其他许多基对的功能还不清楚。

    The majority of human genes have two or more possible , which are alternative forms of a gene. Differences in alleles account for the considerable among people. In fact, most human genetic variation is the result of differences in individual DNA bases within alleles.
    ::大多数人类基因有两种或两种以上的可能性,这些基因是一种基因的替代形式,异形差异是人与人之间的巨大差异。 事实上,大多数人类基因差异是异系内个体DNA基础差异的结果。

     

     

    Summary
    ::摘要

    • Humans have 23 pairs of chromosomes. Of these, 22 pairs are autosomes.
      ::人类有23对染色体 其中22对是异体
    • The X and Y chromosomes are the sex chromosomes. Females have two X chromosomes, and males have one X and one Y.
      ::X和Y染色体是性染色体,女性有两个X染色体,男性有一个X和一个Y。
    • Human chromosomes contain a total of 20,000 to 22,000 genes, the majority of which have two or more alleles.
      ::人类染色体共含有20,000至22,000个基因,其中多数具有两个或两个以上的异形。

    Review
    ::回顾

    1. Describe human chromosomes.
      ::描述人类染色体。
    2. Compare and contrast human autosomes and sex chromosomes.
      ::比较和对比人类的异体 和性染色体
    3. What is SRY?
      ::什么是SRY? (SRY: SRY: SRY: SRY: SRY: SRY: SRY: SRY: SRY: SRY: SRY: SRY)什么是SRY?
    4. Why are females the "default sex" of the human species?
      ::为什么女性是人类的“默认性别”呢?