Section outline

  • General

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  • 游戏起源

    What you will learn
    ::你会学到什么

    • How gametes are formed through spermatogenesis and oogenesis
      ::如何通过精子产生和卵产生来形成调子

    Three ostrich eggs resting on the ground, highlighting their size and unique texture.

    What's the biggest cell on Earth?
    ::地球上最大的细胞是什么?

    The ostrich egg - unfertilized, of course. Yes, this egg, just like a human ovum , is just one . The egg shell membrane encloses the containing the genetic material and the cytoplasm .
    ::当然,这个蛋,就像人类卵卵一样,只是一颗。蛋壳膜包含了遗传物质和细胞图层。

    Gametogenesis
    ::游戏起源

    At the end of , four haploid cells have been produced, but the cells are not yet gametes. The cells need to develop before they become mature gametes capable of . The of haploid cells into gametes is called gametogenesis .
    ::在 + 的末尾, 已经生产了四个杂交单元格, 但单元格还不是调子。 单元格需要开发, 才能成为成熟的调子 。 将杂交单元格变成调子, 称为调子起源 。

    Several sperm cells are shown, illustrating their structure and function in gametogenesis.
    How much DNA is in a gamete? The sperm cell forms by meiosis and spermatogenesis. Because it forms by meiosis, the sperm cell has only half as much DNA as a body cell. Notice the three distinct segments: a head piece, a flagella tail and a midpiece of mostly mitochondria. What is the role of each section?

    Gametogenesis may differ between males and females. Male gametes are called . Female gametes are called eggs . In human males, for example, the process that produces mature sperm cells is called spermatogenesis . During this process, sperm cells grow a tail and gain the ability to “swim,” like the human sperm cell shown in the Figure . In human females, the process that produces mature eggs is called oogenesis . Just one egg is produced from the four haploid cells that result from meiosis. The single egg is a very large cell, as you can see from the human egg in the Figure .
    ::男女的基因起源可能有所不同。 男性调子被称为 。 女性调子被称为 蛋。 例如, 在人类中, 产生成熟精子细胞的过程被称为 精子产生。 在这一过程中, 精子细胞会长尾巴并获得“ 丝子” 的能力, 就像图中显示的人类精子细胞。 在人类女性中, 产生成熟蛋的过程被称为 卵子。 只有一个蛋是来自由美化产生的四个手动细胞。 单蛋是一个非常大的细胞, 从图中的人类蛋中可以看到这一点 。

    A sperm cell approaching a human egg, showing distinct parts: head, tail, and midpiece.
    A human sperm is a tiny cell with a tail. A human egg is much larger. Both cells are mature haploid gametes that are capable of fertilization. What process is shown in this photograph? Notice the sperm with the head piece containing the genetic material, a flagella tail that propels the sperm, and a midpiece of mostly mitochondria, supplying ATP.

    Spermatogenesis and Oogenesis
    ::子形起源和发源

    During spermatogenesis, primary spermatocytes go through the first of meiosis to produce secondary spermatocytes . These are haploid cells. Secondary spermatocytes then quickly complete the meiotic division to become spermatids , which are also haploid cells. The four haploid cells produced from meiosis develop a flagellum tail and compact head piece to become mature sperm cells, capable of swimming and fertilizing an egg. The compact head, which has lost most of its cytoplasm, is key in the formation of a streamlined shape. The middle piece of the sperm, connecting the head to the tail, contains many , providing energy to the cell. The sperm cell essentially contributes only to the zygote .
    ::在精子产生期间,初级精子解剖细胞经过第一种溶解过程,产生次生精子细胞。这些细胞是手动细胞。次精子解剖细胞随后迅速完成微微分,成为精子养分,这些细胞也是手动细胞。由梅西生成的4个手动细胞形成一个尾巴和紧凑头片,成为成熟的精子细胞,能够游泳和给卵子施肥。紧凑头已经失去大部分的细胞,是形成精密形状的关键。精子中间部分,将头与尾部连接起来,含有许多能量,为细胞提供能量。精子细胞基本上只对zygote作出贡献。

    On the other hand, the egg provides the other half of the DNA, but also , building blocks for compounds such as and , and other necessary materials. The egg, being much larger than a sperm cell, contains almost all of the cytoplasm a developing embryo will have during its first few days of life. Therefore, oogenesis is a much more complicated process than spermatogenesis.
    ::另一方面,蛋提供了另外一半的DNA,但也提供了诸如和(......)等化合物和其他必要材料的构件。 蛋比精子细胞大得多,几乎包含了发育中的胚胎在其生命的最初几天里将拥有的所有细胞。 因此,卵的产生比精子产生要复杂得多。

    Oogenesis begins before birth and is not completed until after fertilization. Oogenesis begins when oogonia (singular, oogonium), which are the immature eggs that form in the ovaries before birth and have the diploid number of , undergo to form primary oocytes , also with the diploid number. Oogenesis proceeds as a primary oocyte undergoes the first cell division of meiosis to form secondary oocytes with the haploid number of chromosomes. A secondary oocyte only undergoes the second meiotic cell division to form a haploid ovum if it is fertilized by a sperm. The one egg cell that results from meiosis contains most of the cytoplasm, nutrients , and organelles. This unequal distribution of materials produces one large cell, and one cell with little more than DNA. This other cell, known as a polar body , eventually breaks down. The larger cell undergoes meiosis II, once again producing a large cell and a polar body. The large cell develops into the mature gamete, called an ovum ( Figure ). The unequal distribution of the cytoplasm during oogenesis is necessary as the zygote that results from fertilization receives all of its cytoplasm from the egg. So the egg needs to have as much cytoplasm as possible.
    ::开始于出生前, 并且直到受精之后才完成。 开始于Oogonia ( singal, ogonium) , ogonia (singal, ogonium) 即出生前卵巢中形成的不成熟的卵蛋, 即产卵前的卵蛋, 并具有小卵数, 实验以形成初级卵细胞。 原始卵细胞的产生过程以原始卵细胞细胞的最初分解形式开始, 以染色体的分数形成第二细胞细胞细胞。 大型细胞仅经历第二个细胞的分解, 如果由精子发酵, 则形成一个卵卵。 一个蛋细胞的分解过程包括大部分细胞、 营养和机体。 这种材料的不均匀分布产生一个大细胞, 一个小于DNA的细胞。 另一细胞, 被称为极地体, 最终破裂。 更大的细胞细胞二号, 再一次生成一个大细胞和极体。 大细胞从成熟的细胞发展成卵组, 其变化结果被称为不平等的卵体。 卵体的分化结果 。 。 。 在卵变化过程中, 可能的卵变化过程中, 成的卵变化结果是 。

    Oogenesis and Spermatogenesis                    
    ::发源和发源

     
    • Flowchart illustrating oogenesis stages, detailing meiosis and polar body formation.
    • Flowchart showing stages of spermatogenesis from spermatogonium to sperm.
    Maturation of the ovum and sperms. Notice only one mature ovum, or egg, forms during meiosis from the primary oocyte. Three polar bodies may form during oogenesis. These polar bodies will not form mature gametes. Conversely, four haploid spermatids form during meiosis from the primary spermatocyte.

     

    DID YOU KNOW?
    Oogenesis begins in the fetus and all the primary oocytes are formed prior to birth. After a prolonged growth phase, a single mature ovum is released in a cyclic manner after . In contrast, spermatogenesis begins at puberty, and spermatocytes are continuously created. 
     

     

     

     

     

    Summary
    ::摘要

    • At the end of meiosis, four haploid cells have been produced, but the cells are not yet gametes. The development of haploid cells into gametes is called gametogenesis.
      ::在梅思底部,已经生产了四个手动细胞,但细胞还不是网格。 将手动细胞发展成网格被称为“游戏起源 ” 。
    • Spermatogenesis produces four haploid sperm cells, while oogenesis produces one mature ovum.
      ::Spermato 产生产生 4 条状精子细胞, 而 ocreate 产生一个成熟的卵巢。

    Review
    ::回顾

    1. What is gametogenesis, and when does it occur?
      ::什么是游戏起源,何时发生?
    2. What are the main differences between oogenesis and spermatogenesis?
      ::水的产生和精子的产生之间有什么主要区别?
    3. How many chromosomes are in a human oogonia?
      ::有多少染色体在人类食堂里?
    4. Why is there unequal distribution of the cytoplasm during oogenesis?
      ::为什么在幼年时期细胞顶层的分布不均?