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An asymmetrical division is not like that, it's when a parent cell forms two cells that are different in some way.
而不对称分裂就不是这样,当母细胞分裂为两个子细胞时,会有一些不同
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It might be a plasmid that contains a promoter that works in lung cells and that has the cystic fibrosis gene.
这个质粒带有,可以在肺细胞表达的启动子和正常基因
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What's the difference between this cell which I call a committed progenitor cell and its offspring, and the offspring of that offspring.
我所称的定向祖细胞,和它的子细胞之间,还有它子细胞的子细胞之间有什么区别呢
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That difference has functional consequences for the daughter cells in that one of the daughter cells becomes what's called here a committed progenitor cell.
而这些差异会导致子细胞,产生一些功能上的变化,其中一个子细胞会成为,所谓的定向祖细胞
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Mitosis is an orderly sequence of events by which one parent cell becomes two daughter cells.
有丝分裂是指一个亲代细胞,变为两个子细胞的有序的过程
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It's not self-renewing, in that division of the zygote results in two daughter cells that are no longer the zygote anymore, they're down some pathway.
它是不会自我更新的,受精卵分裂后成了两个子细胞,而这两个子细胞就不再是受精卵了,它们沿着某种路径进行了分化
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We'll talk more about promoters as they go on, for now let's just assume that we have a promoter that works in this particular cell.
我们以后还会谈到更多有关启动子的知识,而现在就假设这个,特定的宿主细胞里有个启动子
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It also has to have a promoter for the gene that the cells can recognize.
另外还必须带有,受体细胞能够识别的启动子
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Well, what if this division takes place in an environment where there's one kind of extra cellular matrix here and another kind of extracellular matrix here?
那如果在细胞分裂的过程中,两个子细胞的细胞外基质不同,会对它们产生什么影响
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When I talked about mitosis, I talked about cells making perfect copies of each other, so each parent cell becoming two daughter cells that are the same.
我讲有丝分裂的时候,谈到过细胞能够完美的复制自己,母细胞分裂成为,两个完全一样的子细胞
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The size of the cells could be different; maybe mitosis is asymmetrical in some way so that one of the cells ends up being bigger than the other.
细胞大小可能会不同,也许有丝分裂的过程是不对称的,致使子细胞一个大一个小
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We talked about the parent cell forming two identical daughter cells.
我们说到母细胞,分裂成为两个一模一样的子细胞
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In terms of function they're very important because this stem cell which is produced goes back into the population of stem cells and is able to repeat this process to form new committed progenitor cells and to form new stem cells.
但就功能而言这些干细胞则至关重要,因为这类分裂产生的子细胞,依然是干细胞,可以再次重复上述步骤,生成新的定向祖细胞,和新的干细胞
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So presumably, these two cells have exactly the same DNA content, but something's been passed onto this one that wasn't there.
按照预计,这两个子细胞应该有完全相同的DNA,但某种成分传给了一个细胞而不是另一个
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If the DNA is synthesized exactly correctly, so each one gets the right copies of DNA, what other differences could there be?
如果DNA的合成精确无误,每个子细胞都有一套相同的DNA,那会有什么其他的不同点呢
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Now when we put insulin in this place behind the right promoter, the cell thinks that it still has the lacZ gene present which it needs for its metabolism.
现在我们把胰岛素基因,放在正确的启动子后面,宿主细胞就会认为,它仍然有新陈代谢所需的lacZ基因
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There could be differences in the physics of cell division, this process of separating into two cells such that even though they both have the same chromosomes, they both have the same DNA content, maybe one of the cells entraps something that's different than the other cells.
细胞分裂的过程中的确可能会产生差异,在分裂为两个细胞的过程中,尽管两个子细胞含有相同的染色体,含有相同的DNA组成,但也许其中一个细胞,截留了和其他细胞不同的物质
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