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Retroviruses, for example, can only insert - can only transduce and express their DNA in cells that are dividing.
就以逆转录病毒为例,它们只能在分裂阶段的细胞里,转导并表达自己的基因
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We talked about mitosis last time; it's described more completely in the chapter, where two cells are formed from one.
我们上节课说到过有丝分裂,在那一章里更详细的阐释了,细胞是怎么由一生二的
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There's nothing in biology per se that rules out cell division.
生物学中没有排除细胞分裂的铁规则。
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It's really just the result of the virus dividing within cells of your skin, and producing a lot of dead cells.
这便是病毒在皮肤细胞内部,分裂的结果,这个过程会产生大量的死亡细胞
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Once you have a difference that occurs, two cells are difference, those differences can propagate as the cells continue to divide.
一旦产生差异,产生两个不同的细胞,这些差异会伴随着,细胞分裂过程代代相传
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It was a gene that was causing a cell to be malignant and to divide without control, for example.
例如,一个会使细胞恶化,并不受控制地无限分裂的基因
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A capability for asymmetric division and the production of cells that become differentiating more mature cells, those are properties of stem cells.
能够完成不对称分裂,以及产生细胞,并分化成为一些更成熟的细胞,这些是干细胞的性质
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This process of cell proliferation or cell division is, of course, very important during development of an embryo.
细胞增殖和分裂的过程,在胚胎发育中至关重要
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So, in general, when cells are proliferating they're dividing and they're dividing at a regular rate.
因此,大致而言,当细胞增殖时,它们是在分裂,并以受调控的频率分裂
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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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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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They can insert genes into non-dividing cells and cause those genes to be expressed.
它使基因导入没有分裂的细胞,并使其表达
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Mitosis is one event that happens during this larger event called the cell cycle.
有丝分裂就是发生在,较大的细胞周期中的一个小一点的环节
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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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Those billions of cells come from successive rounds of cell division.
这数以十亿计的细胞,都来自一次次的细胞分裂
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Well, it might be that this signal is a signal to divide.
这可能是那些让细胞开始分裂的信号
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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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One result of this asymmetrical division is a committed progenitor cell.
这种不对称分裂的一个结果,是产生定向的祖细胞
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It's time for you to reproduce', and so the cellular response would be mitosis.
该是复制的时候了",细胞就开始进行有丝分裂
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We talked about last time that part of the process of going from this single cell to multi cellular many celled organisms like we are is cell division.
我们上节课说过,从一个单细胞分裂形成大量细胞,构成的器官的过程,叫做细胞分裂
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There's one division, here it shows it at the 16 cell stage and then here, and this transformation as it goes from 16 cells to more like 64 cells.
这是第一次分裂,这里显示的是十六细胞期,然后在这里,在这里胚胎进一步的产生了变化,由十六个细胞分裂为约六十四个
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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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They can transduce non-dividing cells so that's a good part.
能够很好的转导非分裂的细胞,这很好
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It goes - going through this process of amplifying divisions, every division increasing the number of cells by a factor of two and these cells becoming more differentiated around the way.
它经历了一系列扩增性的分裂过程,每次分化,细胞数目都翻一番,而在此过程中细胞分化得更成熟
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There are cells within your body that are always in the process of division and forming new cells, and sometimes this is for a tissue where cells only have a finite lifetime.
你体内的一些细胞,始终在不断分裂,并生成新的细胞,很多时候,是在一些细胞寿命有限的组织中
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In the time it takes for one cell division to occur, it could be that this cell entraps a different chemical composition of the cytoplasm then this entraps, and that's a well known concept.
当一个细胞分裂发生期间,很可能这个细胞截留了一种不同的,细胞质化学组分,这种非对称分裂是一个广为人知的概念
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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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The same thing with these cells here, as these cells undergo continual divisions, they're changing in ways that make them mature, that make them more like the mature cells of the nervous system, for example, if that's where they end up being but they're losing potential as they go through that differentiation process.
细胞也是这样,在连续分裂的过程中,它们愈发成熟,比如说,变得越来越像,神经系统细胞,如果它们最终将构成神经系统的话,那它们在分化的过程中,就失去了许多潜能
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If mitosis occurs the way that it's supposed to, the DNA that's in each of these cells is the same.
如果有丝分裂的过程按部就班地进行,那所有细胞的DNA都是相同的
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