李贝贝专业英语第八课第三段资料.ppt

Cleavage: An Increase in Cell Number 卵裂：细胞数量的增加 Cleavage, the major developmental event immediately following fertilization, is a special form of cell division (mitosis). 受精后，立即发生卵裂，细胞分裂（有丝分裂）的特殊过程。 Cleavage [‘kli:vid?] n. 劈开，分裂；[晶体] 解理；[胚] 卵裂 Fertilization [,f??t?la?ze??(?)n] n.[农] 施肥；[胚] 受精；肥沃 Cleavage produces a blastula, a sheet of cells rounded into a sphere that in most species surrounds a cavity. 卵裂产生囊胚，多数种类的一层细胞围成球形，形成一个空腔。 1、blastula[‘bl?stj?l?] n. [胚] 囊胚，囊胚泡 2、sphere[sf??] n. 范围；球体 vt. 包围；放入球内；使…成球形 adj.球体的 3、cavity[‘k?v?t?] n. 腔；洞，凹处 4、a sheet of 一张，一片（例如：a great sheet of water ） In the process, the single-celled zygote is divided into many small cells, and yolk, mRNA, ribosomes, and other materials are distributed to each cell in precise ways. 在这个过程中，单细胞的受精卵分裂成许多小细胞，卵黄，mRNA，核糖体和其他物质被精确分配到每个细胞中。 1、zygote[za?g??t] n. 受精卵；接合子 2、be divided into 被分为（be divided into two parts） 3、be distributed to 被分配给 4、in precise ways 以精确的方式 The cells of the blastula, called blastomeres, also each receive a full diploid set of chromosomes. 这些囊胚细胞，称卵裂球，每个细胞都有一套二倍体染色体组。 1、blastomere[bl?st?(?)m??] n. 分裂球；胚叶细胞 2、diploid[‘d?pl??d] adj. 双倍的；倍数的；双重的 n. [遗] 二倍体；倍数染色体 3、a set of 一套；一组；一副 There are different patterns of cleavage in different species. 不同物种，卵裂方式不同。 The amount of yolk present in the egg is a major factor in determining the pattern: in species having little yolk (such as mammals) the zygote cleaves completely through, forming cells that are roughly equivalent in size. 卵中卵黄含量多少是决定卵裂类型的主要因素。含有少量卵黄的物种（例如哺乳动物），合子分裂得很彻底，子细胞大致平均分裂。 1、equivalent[?kw?v(?)l(?)nt] adj. 等价的，相等的；同意义的 n. 等价物，相等物 2、the amount of ……的数量 In frogs, i