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1、2018/12/10,1,Lesson three,Cellular reproduction: mitosis and meiosis,2018/12/10,2,repository rp:zt:ri n.贮藏室, 智囊团, 知识库, 仓库 chromosome n.生物染色体 histone n.生化组蛋白 nucleosome n.生化核小体 chromatin n.核染质, 染色质 pictorial adj.图示的 n.画报 karyotype n.生物 染色体组型 homologous pair 同源染色体对 autosome n.正染色体, 常染色体,2018/12/10,3,d
2、iploid adj.双重的, n.二倍体 haploid n.生物单倍体 adj.单一的 immortal adj.不朽的 Chalone kln n.生化抑素 prophase n. (细胞分裂)前期 chromatid n.生物染色单体 centromere n.生着丝点, 着丝粒 metaphase n.中期 anaphase n.生(细胞分裂的)后期,2018/12/10,4,Telophase n.生(细胞有丝分裂的)末期 kinetochore kni:tk n.生动粒, 着丝粒, 着丝点 cytokinesis n.细胞浆移动, 原浆移动 pinching v.收聚 cell
3、plate 细胞板 mitosis n.有丝分裂 meiosis n.减数分裂, 成熟分裂,2018/12/10,5,Halving h:v 对分, 二等分, 减半 Synapsis 联会 synaptinemal snptneml complex 联会复合物 Asexual adj.无性的, 无性生殖的 catastrophic adj.悲惨的, 灾难的 Elimination n.排除, 除去, 消除, 消灭,2018/12/10,6,1. The nucleus and chromosomes,2018/12/10,7,The cell nucleus is the main repos
4、itory of genetic information. 细胞核是贮藏遗传信息的主要场所。 Within the nucleus are the chromosomestightly coiled strands of DNA and clusters of associated proteins. 细胞核里的是染色体紧密盘绕成螺旋的DNA链和相关的成簇蛋白质。,2018/12/10,8,Long stretches of the continuous DNA molecule wind around these clusters of proteins, or histones, form
5、ing beadlike complexes known as nucleosomes. 长链DNA分子缠绕着成簇的蛋白质，或组蛋白，形成珠链状的核小体。,2018/12/10,9,More coiling and supercoiling produces a dense chromosome structure. 进一步的螺旋和超螺旋形成致密的染色体组结构。 Each long strand of DNA combine with histones and nonhistone proteins to make up the substance chromatin. 每个长链DNA与组蛋白
6、和非组蛋白一起构成染色质物质。,2018/12/10,10,A pictorial display of an organisms chromosomes in the coiled, condensed state is known as a karyotype. 生物体中的致密的超螺旋状态的染色体的表型称为核型 Karyotype reveal that in most cells all but sex chromosomes are present as two copies, referred to as homologous pairs. 表型显示：在大多数细胞里，除了性染色体外，
7、其它的染色体都是成对出现的，称之为同源染色体对。,2018/12/10,11,Non-sex chromosomes are called autosomes. 非性染色体称常染色体。 Organisms whose cells contain two sets of parental chromosomes are called diploid; those with cells containing a single set of parental chromosomes are called haploid. 细胞里含有两套亲本染色体的生物体称二倍体；细胞里含有单套染色体的生物体称单倍体
8、。,2018/12/10,12,2018/12/10,13,2. The cell cycle 细胞周期,2018/12/10,14,The cell cycle is a regular sequence in which the cell grows, prepares for division, and divides to form two daughter cells, each of which then repeats the cycle. 细胞周期遵循特定的程序：细胞生长，分裂准备，分裂成2个子细胞，每个子细胞再循环。 Such cycling in effect makes
9、single-celled organisms immortal. 此循环可以有效的使得单细胞生物永生。,2018/12/10,15,Many cells in multicellular organisms, including animal muscle and nerve cells, either slow the cycle or break out of it altogether. 多细胞生物中的许多细胞，包括动物肌肉和神经细胞，要么减慢周期速度，要么一起脱离细胞周期。 The normal cell cycle consists of four phases. 正常细胞周期由4
10、个时期组成。,2018/12/10,16,The first three include G1, the period of normal metabolism; S phase, during which normal synthesis of biological molecules continues, DNA is replicated, and histones are synthesized; and G2, a brief period of metabolism and additional growth. 前三个时期包括G1,正常新陈代谢时期；S期, 生物分子的合成继续，同时
11、，DNA复制，组蛋白合成； G2 期，新陈代谢和进一步生长的短暂时期。 Together the G1, S, and G2 phases are called interphase. G1, S, 和G2一起称为分裂间期。,2018/12/10,17,The fourth phase of the cell cycle is M phase, the period of mitosis, during which the replicated chromosomes condense and move and the cell divides. 细胞周期的第四个时期是M期，有丝分裂期，复制的
12、染色体浓缩，移动并细胞分裂。,2018/12/10,18,It is believed that properties of the cell cytoplasm control the cell cycle, along with external stimulators and inhibitors such as chalones. 据称是细胞质中的物质与外来的激活因子和抑制因子如抑素等一起控制了细胞周期。,2018/12/10,20,3. Mitosis: partitioning the hereditary material 有丝分裂： 遗传物质的分离,2018/12/10,21,
13、Biologists divide the mitotic cycle into four phases. 生物学家将有丝分裂划分为4个阶段。 At the beginning of prophase the chromosomes each consist of two highly condensed chromatids attached to each other at a centromere. 分裂前期，每个染色体是由高度浓缩的通过着丝粒连接在一起的两个染色单体组成。(分裂前期，高度浓缩的两个染色单体通过着丝粒连接在一起形成染色体),2018/12/10,22,As prophas
14、e ends and metaphase begins, the condensed chromosomes become associated with the spindle. 分裂前期结束，紧接着是分裂中期，浓缩的染色体与纺锤体相连。(在分裂前期后期和分裂中期前期，浓缩的染色体与纺锤体相连) Eventually the chromosomes become arranged in a plane (called the metaphase plate) at a right angle to the spindle fiber. 最后染色体在纺锤丝的牵引下以正确的角度排列在赤道板上。,
15、2018/12/10,23,Next, during anaphase, the two sister chromatids of each chromosome split, and one from each pair is drawn toward each pole of the cell. 在分裂后期，两个姊妹染色单体分离，分别被拉向细胞两极。 During telophase nuclear envelope begin to form around each set of chromosomes, and division of the cytoplasm takes place
16、. 在分裂末期，在每套染色体周围形成核膜，细胞质分裂发生。,2018/12/10,24,As mitosis proceeds, the spindle microtubules play a crucial role in ensuring that both paired and separated chromatids move in the right directions at the proper times. 在有丝分裂过程中，纺锤体微管在确保染色单体配对和在适当时间以正确方向进行分离中发挥了关键性的作用。 Each half of the spindle forms as microtubules extend from each pole of a dividing cell to the region of the metaphase plate. 微管从正在分裂的细胞两极向赤道板延伸，就形成了纺锤体的一半。,2018/12/10,25,During p
