生物工程专业英语（Bioengineering English）
As in mitosis two chromatids exist for each chromosome at the beginning of prophase 1. During this phase the homologous 同源 chromosomes undergo 经历sy-napsis 联会 , or pairing, which is brought about by a bridging structure of proteins and RNA called the synaptonemal 联会丝的 complex. The homologous pairs stay together when they align 排列 on the metaphase 中 plate. Unlike the anaphase of mitosis, however, during anaphase I the two chromatids of each chromosome stay joined at the centromere 着丝点 and move together to one of the two poles of the cell. It is this event that results in the halving 减半的 of the chromosome number in the four daughter cells that result from meiosis.
正如在有丝分裂中一样，两个同源染色单体通过蛋白质和RNA桥配对形成联会复合体。与有丝分裂不同的是，每组染色体的两个染色单体连接在着丝点上并一起移向细胞两极的一级。由此而导致4个子细胞染色体数减半。
During telophase末期 I nuclear envelopes enclose the chromosomes in nuclei, and in most species cytokinesis 细胞浆流动 (the first nuclear division) follows. The second nuclear division begins with metaphase Ⅱ, in which the chromosomes in each daughter cell again align 排列on a metaphase plate. The centromeres着丝粒 finally divide, and each sister chromatid moves to one of the poles of the spindle. The next phase is telophase , followed again by cytokinesis. The result of the entire process is four haploid cells in which parental chromosomes are randomly distributed.
第二次核分裂开始于分裂中期，子细胞中染色体重新排列在赤道板上。着丝粒最终分离，每个姊妹染色单体分向两极。接着胞质分裂。产生4个单倍体，父母染色体随机分配。 Asexual Versus Sexual Reproduction
Mitosis and meiosis, respectively分别, make simple cell division and sexual reproduction possible. Each means of passing on hereditary 遗传 information has advantages. In asexual 无性的 reproduction the parent organism生物体 gives rise to offspring 后代that are genetic clones of the parent. The advantages of this type of reproduction are that it preserves the
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生物工程专业英语（Bioengineering English）
parent's successful genetic complement 遗传互补, requires little or no specialization of reproductive organs, and is more rapid than sexual reproduction. A major disadvantage of the asexual mode is that a single catastrophic灾难的 event or disease may destroy an entire population of genetically identical organisms. A prime benefit of sexual reproduction is that it provides genetic variability and a ready mechanism机制 for the elimination of deleterious mutations. It also allows \
有丝分裂和减数分裂在传递遗传信息过程中各有优势。体细胞的繁殖就是父母本的克隆，其优势是保留了父母本的成功遗传信息，不需要特殊器官，比性复制快的多。但一个简单灾难性事件或疾病都可能摧毁一个细胞群体。性复制的优势是它提供了遗传可变性和现存排除有害突变的机制。也可以产生新的基因并在种群中蔓延。
课后作业：第一篇阅读材料 答案：1C,2B,3D,4B,5A,6D
Glossary
mitosis 有丝分裂
Process that results in equal and identical distribution of replicated chromosomes into two newly formed nuclei. meiosis 减数分裂
The process by which a nucleus divides into four daughter nuclei, each containing half the number of chromosomes of the parent nucleus.
histone 组蛋白
One of a group of simple proteins that have a high content of the basic amino acids arginine or lysine and are found
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associated with nucleic acids in the chromatin of eukaryotic cells.
nucleosome 核小体
The basic unit of chromatin structure in eukaryotic cells. A nucleosome consists of eight histone molecules of four different types, together with about 140 base pairs of DNA coiled around it.
chromatin 染色质
The material of which the chromosomes are composed. DNA and protein are the main constituents of chromatin, most of the protein being histone.
karyotype 核型，染色体组型 ,
生物工程专业英语（Bioengineering English）
The appearance of the chromosome complement of an organism or cell. homologous pair 同源染色体对
Chromosomes that pair during meiosis. Each homologue is a duplicate of one of the chromosomes contributed at syngamy by the mother or father. Homologous chromosomes contain the same linear sequence of genes and as a consequence each gene is present in duplicate. diploid二倍体
Any nucleus, cell, or organism that possesses twice the haploid number of chromosomes. haploid 单倍体
Any nucleus, cell, or organism that possesses a single set of unpaired chromosomes,
interphase (cycle) 分裂间期（周期） In a cell preparing to duplicate, the interphase stage can divided into a period of initial growth (G1), a period of DNA synthesis (S), and a second growth period (G2).
chalone 抑素
Substances found in mammalian tissue homogenates that, when applied to intact tissue cells, inhibit mitosis, particularly in the presence of adrenaline and corticosteroids.
prophase （分裂）前期
First stage of mitosis, during which individual chromosomes become visible.
chromatid 染色单体
A replicated chromosome physically attached to an identical chromatid at the centromere. centromere 着丝粒
The small area of a chromosome that does not stain with basic dyes during mitosis and meiosis; at interphase it is single while the rest of the chromosome is made up of two chromatids. metaphase （分裂）中期
Second stage in mitosis, during which the chromosomes align at the equatorial plane.
spindle 纺锤体
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生物工程专业英语（Bioengineering English）
An array of microtubutes extending from pole to pole and used in the movement of chromosomes.
anaphase 分裂后期
The third stage of mitosis, during which the centromeres split and the chromosomes move to the poles.
telophase （分裂）末期
metaphase plate 赤道板，中期板
The grouping of the chromosomes in a plane at the equator of the spindle during the metaphase stage of mitosis.
cytokinesis 胞质分裂
cell plate 细胞板
Last stage in mitosis during which daughter nuclei are formed.
Division of the cytoplasm of one cell into two new cells.
A plant cell structure that begins to form in the center of the cell and proceeds to the cell membrane, resulting in cytokinesis.
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生物工程专业英语（Bioengineering English）
Lesson Four（2学时）
Foundations of Genetics
教学目的：使学生了解遗传学的发展历程，掌握孟德尔遗传学的建立及经典实验。相关英语词汇以及主要用法。
教学重点：孟德尔遗传学的两个定律，及相关英语词汇的掌握 教学难点：专业英语词汇的记忆
讲授方法：以学生翻译为主，老师讲解相关专业知识辅助学生理解 授课时间：4月19日 教学内容：
Early Theories of inheritanee
Early ideas of inheritance included Hippocrates' theory of pangenesis and August Weismands germ plasm theory. Based on experiments with mice, Weismann proposed that hereditary information in gametes transmitted traits to progeny. Both of these early views incorporated the blending theory: they held that heritable traits of the two parents blend, so that the distinct characteristics of each are lost in offspring.
遗传学的早期理论包括泛生说和种质理论。基于小鼠实验，维丝曼提出遗传信息储存在配子中并将遗传信息传递给后代。这两个早期观点合起来形成融合理论：子代拥有父母本混合的遗传特征，而不完全象亲代。
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