Lesson Three（2學時） Cellular Reproduction: Mitosis and Meiosis 教學目的：使學生掌握細胞的有絲分裂和無絲分裂的作用機理，有絲分裂和無絲分裂之間的區別和相同點。相關英語詞匯以及主要用法。教學重點：有絲分裂和無絲分裂中相關的概念和功能，及相關英語詞匯的掌握教學難點：專業英語詞匯的記憶講授方法：以學生翻譯為主，老師講解相關專業知識輔助學生理解授課時間：4月12日教學內容：
The Nucleus and ChromosomesThe cell nucleus is the main repository of genetic information. Within the nucleus are the chromosomes tightly coiled strands of DNA and clusters of associated proteins. Long stretches of the continuous DNA molecule wind around these clusters of proteins, or histones, forming beadlike complexes known as nucleosomes. More coiling and supercoiling produces a dense chromosome structure. Each long strand of DNA combines with histones and nonhistone proteins to make up the substance chromatin.細胞核是貯藏遺傳信息的主要場所。DNA盤繞成螺旋線以及相關的成簇蛋白質。DNA螺旋線纏繞成簇的組蛋白形成珠鏈狀的核小體。這些螺旋和超螺旋形成致密的染色體組結構。每個長鏈DNA與組蛋白和非組蛋白一起構成染色質物質。
A pictorial display of an organism's chromosomes in the coiled, condensed state is known as a karyotype. Karyotype reveal that in most cells all but sex chromosomes are present as two copies, referred to as homologous pairs. Non-sex chromosomes are called autosomes. 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. 染色體致密的超螺旋狀態我們稱染色體組。除了性染色體外，大多數細胞的染色體組成對出現，稱同源染色體對。非性染色體稱常染色體。生物細胞含有兩套父母本染色體的稱二倍體；含有單套染色體的稱單倍體。
The Cell CycleThe 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. Such cycling in effect makes single-celled organisms immortal. Many cells in multicellular organisms, including animal muscle and nerve cells, either slow the cycle or break out of it altogether.在細胞生長過程中，細胞循環遵循特定程序，分裂準備，分裂成2個子細胞，子細胞再循環。此循環使得單細胞永生。多細胞生物中的許多細胞，包括動物肌肉和神經細胞，要么降低循環速度，要么同時分裂。
The normal cell cycle consists of four phases. 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. Together the G1, S, and G2 phases are called interphase. 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. It is believed that properties of the cell cytoplasm control the cell cycle, along with external stimulators and inhibitors such as chalones.
正常細胞循環由4個時期組成。頭三期包括G1,正常新陳代謝；S期,正常新陳代謝同時，DNA復制，組蛋白合成； G2 期，短期的新陳代謝和少許生長。G1, S, 和G2稱分裂間期。最后是M期，有絲分裂期，復制的染色體組濃縮，移動并細胞分裂。據稱是染色質控制了細胞循環，伴隨外部激活因子和抑制因子如抑素。
Mitosis: Partitioning the Hereditary MaterialBiologists divide the mitotic cycle into four phases. At the beginning of prophase the chromosomes each consist of two highly condensed chromatids attached to each other at a centromere. As prophase ends and metaphase begins, the condensed chromosomes become associated with the spindle. Eventually the chromosomes become