李貝貝專業(yè)英語(yǔ)第八課第三段

1、Cleavage: An Increase in Cell Number卵裂：細(xì)胞數(shù)量的增加 Cleavage, the major developmental event immediately following fertilization, is a special form of cell division (mitosis). 受精后，立即發(fā)生卵裂，細(xì)胞分裂（有絲分裂）受精后，立即發(fā)生卵裂，細(xì)胞分裂（有絲分裂）的特殊過(guò)程的特殊過(guò)程。 Cleavage kli:vid n. 劈開，分裂；晶體 解理；胚 卵裂 Fertilization ,ftlaze()n n.農(nóng) 施肥；胚 受精；肥沃

2、lCleavage produces a blastula, a sheet of cells rounded into a sphere that in most species surrounds a cavity. l卵裂產(chǎn)生囊胚，多數(shù)種類的一層細(xì)胞圍成球形，形卵裂產(chǎn)生囊胚，多數(shù)種類的一層細(xì)胞圍成球形，形成一個(gè)空腔。成一個(gè)空腔。1、blastulablstjl n. 胚 囊胚，囊胚泡2、spheresf n. 范圍；球體 vt. 包圍；放入球內(nèi)；使成球形 adj.球體的3、cavitykvt n. 腔；洞，凹處4、a sheet of 一張，一片（例如：a great sheet of

3、water ）nIn 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. n在這個(gè)過(guò)程中，單細(xì)胞的受精卵分裂成許多小細(xì)胞，在這個(gè)過(guò)程中，單細(xì)胞的受精卵分裂成許多小細(xì)胞，卵黃，卵黃，mRNA，核糖體和其他物質(zhì)被精確分配到每，核糖體和其他物質(zhì)被精確分配到每個(gè)細(xì)胞中。個(gè)細(xì)胞中。1、zygotezagt n. 受精卵；接合子2、

4、be divided into 被分為（be divided into two parts）3、be distributed to 被分配給4、in precise ways 以精確的方式The cells of the blastula, called blastomeres, also each receive a full diploid set of chromosomes.這些囊胚細(xì)胞，稱卵裂球，每個(gè)細(xì)胞都有一套二這些囊胚細(xì)胞，稱卵裂球，每個(gè)細(xì)胞都有一套二倍體染色體組。倍體染色體組。1、blastomereblst()m n. 分裂球；胚葉細(xì)胞2、diploiddpld adj. 雙

5、倍的；倍數(shù)的；雙重的 n. 遺 二倍體；倍數(shù)染色體3、a set of 一套；一組；一副There are different patterns of cleavage in different species.不同物種，卵裂方式不同。不同物種，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,

6、 forming cells that are roughly equivalent in size.卵中卵黃含量多少是決定卵裂類型的主要因素。含有少量卵黃卵中卵黃含量多少是決定卵裂類型的主要因素。含有少量卵黃的物種（例如哺乳動(dòng)物），合子分裂得很徹底，子細(xì)胞大致平的物種（例如哺乳動(dòng)物），合子分裂得很徹底，子細(xì)胞大致平均分裂。均分裂。1、equivalentkwv()l()nt adj. 等價(jià)的，相等的；同意義的 n. 等價(jià)物，相等物2、the amount of 的數(shù)量 In frogs, in which the egg has somewhat more yolk, cleavage pr

7、oceeds more rapidly in regions of the embryo having less yolk. In bird eggs the yolk is so massive that cleavage divisions are restricted to a tiny area of cytoplasm.對(duì)于卵黃較多的蛙類而言，在含有較少卵黃的胚胎對(duì)于卵黃較多的蛙類而言，在含有較少卵黃的胚胎區(qū)域卵裂速度更快些。鳥卵卵黃很大，卵裂被限制區(qū)域卵裂速度更快些。鳥卵卵黃很大，卵裂被限制在細(xì)胞質(zhì)很小區(qū)域內(nèi)。在細(xì)胞質(zhì)很小區(qū)域內(nèi)。1、embryoembr n. 胚 胚胎；胚芽；初期

8、 adj. 胚胎的；初期的2、sothat 如此以至于3、be restricted to 僅限于；局限于In many species the precise distribution to blastomeres of molecular determinants in the cytoplasm is crucial to proper development of different cell types in the embryo.對(duì)許多物種而言，細(xì)胞質(zhì)中分子遺傳因素精確分配對(duì)許多物種而言，細(xì)胞質(zhì)中分子遺傳因素精確分配到卵裂球中，是發(fā)育成胚中不同類型細(xì)胞關(guān)鍵所在。到卵裂球中，是發(fā)育成胚中不同類型細(xì)胞關(guān)鍵所在。determinantdtmnnt adj. 決定性的 n. 決定因素is crucial to 對(duì)至關(guān)重要In mammal and bird species the fate of cells is determined by the position