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C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | McEntee, K., Weinstock, G. M. & Lehman, I. R. Proc. Natl. Acad. Sci. U.S.A. 76, 2615-2619 (1979).
Sugino, A., Higgins, N. P., Brown, P. O., Peebles, C.L. & Cozzarelli, N. R. Proc, Natl. Acad. Sci. U.S.A. 75, 4838-4842 (1978).
Clark, A. J. A. Rev. Genet. 7, 67-86 (1973).
Radman, M. in Molecular Mechanisms for Repair of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 最近,柴田等人[4]观察到化学计量定量的高度纯化的recA蛋白可以促进超螺旋DNA和同源的单链DNA片段迅速形成D环(图1)。 英文
非催化的D环的形成仅在非生理温度下迅速发生,表明其反应速率受超螺旋DNA少量碱基对的起始解离的限制[3]。由于recA蛋白不受这一限速步骤的影响,因此我们认为它在某种程度上通过解开双链DNA的配对碱基来发挥作用。我们还观察到,带切口的环状DNA(II型)在与单链DNA片段形成复合物时,其活性只有超螺旋DNA的三分之一[4]。接下来,我们证实了II型DNA是recA蛋白形成D环时的一个底物(见下文)。这一观察结果进一步加强了关于recA蛋白具有解配对或解旋活性的推论,这也是本文的主题。 英文
图1. ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 当反应体系中没有recA蛋白时,约有一半回收的DNA在梯度的高密度区形成的一个单峰里,这与预期中的连接酶将II型DNA闭合而形成I′型DNA的结果吻合(图3b,表1,第1行)。在连接反应前将II型DNA与recA蛋白和ATPγS孵育并不会对这种分布产生什么影响(图3a,表1,第2行)。然而,如果在进行连接反应前把recA蛋白、fd II型DNA、ΦX174单链DNA片段以及ATPγS一起孵育,则位于梯度中最高密度区的I′型DNA的峰几乎完全消失,取而代之的是密度介于I′型DNA与线性或II型DNA之间的广泛分布的峰(图3a,表1,第3行),也就是说,这些DNA的链环数比I′型DNA要低。位于中等密度区域的峰代表负超螺旋fd DNA(... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 环状单链DNA虽然不能够形成D环,但是可以促进双链DNA的解旋(图4d)。双链限制性酶切片段不具有这种活性,但是其煮沸后的产物则可以促进双链DNA的解旋(图4f,g)。这些观察结果表明,解旋的辅因子不是DNA样品的某些偶然性成分。使用胰DNA酶消化并煮沸处理产生的全部酸溶性产物也具有很好的促进解旋活性(图4e)。而脱氧腺苷、dAMP、dGMP、dCMP、dTMP、AMP和CMP单独加入反应体系时,不具有或仅具有很低的促进解旋的活性(数据未展示)。 英文
图4. 琼脂糖凝胶电泳实验结果。当ATPγS存在时,触发recA蛋白发挥解旋作用的辅因子的性质(a~g);recA蛋白不具有拓扑异构酶的活性(l~o)。a~g泳道含有在ATPγS、... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | DNA促旋酶也可以在另一个不能够被水解的ATP类似物存在时催化部分反应的进行[11]。根据II型DNA可以形成D环这一观察结果,我们推断recA蛋白在ATP存在时也可以促进DNA的解螺旋。ATP的水解会引起蛋白质–DNA复合物的改变或者解离,并在ATP和DNA连接酶存在的情况下,抑制部分解旋的DNA的积累(未发表的观察结果)。 英文
初看上去,由异源单链DNA激活的解旋似乎并不适合作为促进同源配对的机制。但是进一步想来,由任意单链DNA非特异性地触发双链DNA解旋可以部分地解释recA蛋白如何促进对同源配对序列的搜寻,因此这一观点是有道理的。由于在大肠杆菌中,同源重组高度依赖于recA蛋白的功能[12],因此recA蛋白在这种机制下... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | within the genome, that is truly “selfish”. The nature of “junk DNA”, and the issue of whether it truly has no role integral to the genome, has become a hot topic of research in the new era of genomics. 中文
Natural selection operating within genomes will inevitably result in the appearance of DNAs with no phenotypic exp... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The phenotype paradigm underlies attempts to explain genome structure. There is a hierarchy of types of explanations we use in efforts to rationalize, in neo-darwinian terms, DNA sequences which do not code for protein. Untranslated messenger RNA sequences which precede, follow or interrupt protein-coding sequences are... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | What we propose here is that there are classes of DNA for which a “different kind of explanation” may well be required. Natural selection does not operate on DNA only through organismal phenotype. Cells themselves are environments in which DNA sequences can replicate, mutate and so evolve21. Although DNA sequences whic... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Most speculations on the function of transposable elements concentrate on the role these may have, through chromosomal rearrangements and the modular assembly of different functional units, in promoting the evolution of plasmid and bacterial chromosomes, and thus in promoting long-term phenotypic fitness12-16. Most ass... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | against deletion. It is significant that recent models for transposition require retention of the parental sequence copy26,27, and that bacterial insertion sequences are characteristically present in several copies per genome16. The assumption that transposable elements are maintained by selection acting on the cell do... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | It is certainly not novel to suggest that prokaryotic transposable elements behave in these ways, or to suggest that more frankly autonomous entities like phages have arisen from them12-16,31. However, we think it has not been sufficiently emphasized that non-phenotypic selection may inevitably give rise to transposabl... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | the elements themselves, rather than for other cellular processes”(ref. 37). But if maintenance and mobility mechanisms exist, then no cellular function at all need be postulated. 中文
A large fraction of many eukaryotic genomes consists of middle-repetitive DNAs, and the variety and patterns of their interspersion with ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | such elements, then the observed spectra of sequence divergence within families and changes in middle-repetitive DNA family sequence and abundance can all be explained as the result of non-phenotypic selection within genomes. No cellular function at all is required to explain either the behaviour or the persistence of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | phenotypically or evolutionarily advantageous roles, has been suggested elsewhere50,51. 中文
Why Do Prokaryotes and Eukaryotes Differ?
It is generally believed that prokaryotic genomes consist almost entirely of unique-sequence DNA maintained by phenotypic selection, whereas the possession of “excess” unique and repetiti... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | this being greatest in organisms for which DNA replication comprises the greatest fraction of total energy expenditure. Prokaryotes in general are smaller and replicate themselves and their DNA more often than eukaryotes (especially complex multicellular eukaryotes). Phenotypic selection pressure for small “streamlined... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Dawkins, R. The Selfish Gene (Oxford University Press, 1976).
Crow, J. F. Scient. Am. 240, 134-146 (1979).
Cox, E. C. & Gibson, T. C. Genetics 77, 169-184 (1974).
Maynard Smith, J. The Evolution of Sex (Cambridge University Press, 1978).
Darnell, J. E. Prog. Nucleic Acid Res. Molec. Biol. 22, 327-353 (1978).
Crick, F. ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Campbell, A. in Biological Regulation and Development Vol. 1 (ed. Goldberger, R. F.) 19-55 (Plenum, New York, 1979).
McClintock, B. Cold Spring Harb. Symp. Quant. Biol. 16, 13-47 (1952).
Cameron, J. R., Loh, E. Y. & Davis, R. W. Cell 16, 739-751 (1979).
Finnegan, D. J., Rubin, G. M., Young, M. W. & Hogness, D. S. Cold ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 毫无疑问,道金斯对这个观点以及自然选择作用于基因本身而不是作用于个体或者种群的观点做出了最强有力和最坚定的最新陈述[1]。尽管我们可能因此将基因和DNA在本质上看作是“自私的”,但是无论如何,大多数人坚持本文我们称为“表型模式”的观点——基因能够确保长期存在的主要或者可能唯一的方法就是确保其寄存的生物体一直存活。尽管诸如果蝇的分节突变位点[2]、大肠杆菌的“搭乘”增变基因[3,4]以及很多物种的孤雌生殖基因[4]等基因都是这样自私,即通过牺牲种群的进化适应性而促进自身的传播,但是它们也是通过表型实现的。 英文
在表型模式的基础上尝试解释基因组结构。从新达尔文主义的角度,我们试图从各个层次给出某些DNA不编码蛋白质的合理解释。这些先于... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 对宿主表型没有益处的单拷贝DNA序列存在被删除的风险,但是在基因组内多个位置存在自身拷贝的序列只能通过多个位点同时缺失才能从基因组中彻底删除。单纯的易位(从一个位点移除插入到另一个位点)不能确保序列免于被删除。很显然,近来的转座模型均需要保留亲本的序列拷贝[26,27],而且细菌的插入序列特征性地在每个基因组内存在多个拷贝[16]。假设转座元件通过作用于细胞的选择而得以保留,这个假设的成立并不需要它们具备这些特征。一个细菌基因组及其后代为代表的环境内的单拷贝转座元件的进化行为同样可以用生物体进化的方式来理解。特定元件的复制拷贝可能分散在序列上,但是至少转座所需序列的特征会通过(非表型)选择保留下来;再也不能易位的拷贝最终会被删除。一... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 另外1%~40%由功能未知的简单重复序列组成[10],并且史密斯认为“串联重复的形式是DNA的天然状态,其序列并不通过选择来保持”(文献47)。甚至组成一大部分元件的真核DNA的单一序列似乎也不受表型选择压力约束[45]。一些作者认为那些使很多真核生物结构基因中断的间隔序列都是类似于插入序列的元件[6,48,49]。如果确实如此,那么它们很可能是转座序列退化并且不再具备转座能力的产物,其插入通过预先存在的细胞RNA–RNA剪接机制呈现非致死性。这些元件,一旦插入后,相对难以被删除(因为只有非常精确的删除才是非致命性的),并且仅需保留那些RNA剪接所需的序列成分。元件的剩余部分可以自由移动,并且可以预期(并观察到),只有同源基因家族内... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
(毛晨晖 翻译;崔巍 审稿)
Selfish DNA: the Ultimate Parasite
L. E. Orgel and F. H. C. Crick
Editor’s Note
In the second of two consecutive review articles on “selfish DNA”, Leslie Orgel and Francis Crick at the Salk Institute in California consider how this form of DNA—which proliferates in the genome without significantly af... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | This idea is not new. We have not attempted to trace it back to its roots. It is sketched briefly but clearly by Dawkins1 in his book The Selfish Gene (page 47). The extended discussion (pages 39-45) after P. M. B. Walker’s article2 in the CIBA volume based on a Symposium on Human Genetics held in June 1978 shows that ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | multiple copies (since, unlike protein, their final products are the result of only one stage of magnification, not two), the majority of genes coding for proteins appear to exist in “single” copies, meaning here one or a few. A typical example would be the genes for α-globin, which occur in one to three copies and the... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | There is also evidence to suggest that the majority of DNA sequences in most higher organisms do not code for protein since they do not occur at all in messenger RNA (for reviews see refs 14, 15). Nor is it very plausible that all this extra DNA is needed for gene control, although some portion of it certainly must be.... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | fairly near together in a single stretch of DNA, occupy a region no less than 40 kilobases long17. This greatly exceeds the total length of the four primary transcripts (that is the four mRNA precursors), an amount estimated to be considerably less than 10 kilobases. There is little evidence to indicate that there are ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | provided certain conditions are satisfied. If an organism carrying several copies of the sequence is fitter than an organism carrying a single copy, and if mechanisms exist for the multiplication of the relevant sequence, then natural selection must lead to the emergence of a population in which the sequence is represe... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | chromosomes. 中文
During mitosis and meiosis, multiplication (or deletion) is likely to occur by unequal crossing over. This mechanism will often lead to the formation of tandem repeats. It is well documented for the tRNA “genes” of Drosophila and for various other tandemly repeated sequences in higher organisms. 中文
The ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | be much smaller. The selective disadvantage might be greater in more stringent conditions, but it is still hard to believe that a relatively small proportion of selfish DNA could be selected against strongly. 中文
On the other hand, when the total amount of selfish DNA becomes comparable to or greater than that of useful... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | is a very long time, so the elimination of a particular stretch of selfish DNA may be a very slow process even on a geological time scale. Second, the mechanisms for the deletion of short sequences of DNA may be inefficient, since there is no strong selective pressure for the development of “corrective” measures when t... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | way. 中文
In short, we may expect a kind of molecular struggle for existence within the DNA of the chromosomes, using the process of natural selection. There is no reason to believe that this is likely to be much simpler or more easy to predict than evolution at any other level. At bottom, the existence of selfish DNA is... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | It would be surprising if the host organism did not occasionally find some use for particular selfish DNA sequences, especially if there were many different sequences widely distributed over the chromosomes. One obvious use, as repeatedly stressed by Britten and Davidson19,20, would be for control purposes at one level... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | On this picture, each set of repeated sequences might be “tested” from time to time in evolution by the production of a control macromolecule (for example, a special protein) to recognize those sequences. If this produced a favourable result, natural selection would confirm and extend the new mechanism. If not, it woul... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Thus, some selfish DNA may acquire a useful function and confer a selective advantage on the organism. Using the analogy of parasitism, slightly harmful infestation may ultimately be transformed into a symbiosis. What we would stress is that not all selfish DNA is likely to become useful. Much of it may have no specifi... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | junk DNA rather than the total DNA content which influences the duration of meiosis. 中文
An analogous situation may obtain in certain American species of salamander. These often differ considerably in the rapidity of their development and of their life cycles, the tropical species tending to take longer than the more te... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Third, one would hope that a careful study of all the nonspecific effects of extra DNA would give us a better idea of how it affected different aspects of cellular behaviour. In particular, it is important to discover whether the addition of nonspecific DNA does, in fact, slow down cells metabolically and for what reas... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | We thank W. Ford Doolittle and C. Sapienza for showing us their article before publication, and Drs D. Wake and H. MacGregor for allowing us to quote some of their unpublished conclusions about salamanders. This work was supported by the Eugene and Estelle Ferhauf Foundation, the J. W. Kieckhefer Foundation, the Ahmans... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Wilson, A. C. in Molecular Evolution (ed. Ayala, F. J.) 225-236 (Sinauer, Sunderland, 1976).
Bennett, M. D. Proc. R. Soc. B181, 109-135 (1972).
Bennett, M. D. & Smith, J. B. Proc. R. Soc. B181, 81-107 (1972).
Young, M. W. Proc. Natl. Acad. Sci. U.S.A. 76, 6274-6278 (1979).
Oeldorfe, E., Nishioka, M. & Bachmann, K. Sond... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 这些作者[13]得出结论“只有一种解释较为合理,在动物的生命过程中许多单拷贝DNA的特异性序列在功能上并不是必需的。这并不是说这些DNA没有功能,只是它的特异序列并不重要。” 英文
同样有证据表明大多数高等生物的大部分DNA序列并不编码蛋白质,因为它们根本不出现在信使RNA中(综述见参考文献14,15)。尽管一部分必定会起到作用,但是要说这些多余的DNA都是基因调控所必需的,也并不合理。 英文
我们还必须解释的是,在某些物种(例如百合和蝾螈)中发现了惊人数量的DNA,其数量约为人类基因组的二十倍。蝾螈所需的完全不同基因的数量是人类的二十倍是完全不合理的假设;而且没有证据表明蝾螈的基因大都存在二十个相当类似的拷贝。所以可以确信,很多这... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 果蝇的tRNA“基因”和高等生物其他各种串联重复序列就是很好的证明。 英文
自私DNA的数量和位点
基因组内的自然选择倾向于自私的优先复制子的无限扩增。基因型间的自然选择提供了一种平衡力使自私DNA的总量保持平衡(稳定状态)——基因组中含过量比例的自私DNA的生物比含较少自私DNA的生物,在新陈代谢方面将处于劣势,因此将在自然选择的正常机制下被淘汰。没有功能的复制子的过度扩增可以看作是基因组的“癌症”——基因组中一个片段不受控制的扩增将最终导致允许这种扩增的基因型的消失。当然,我们甚至不知道自然界中基因型的消失是否是出于这个原因。 英文
在这类问题上得到超出一般性的概括是很困难的。如果要研究,我们至少要知道一定数量无用DNA的存在将... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 这不仅仅是因为增殖机制会以某种形式产生重复序列(见杜利特尔和萨皮恩扎[5]的讨论),还因为这些拷贝很可能分散到染色体各处,而不会像大多数普通基因那样只定位于基因组某个固定的位置。基于这两个原因,一种特殊类型的自私DNA很可能比低选择优势的普通基因在种群中扩增得更快。如果自私DNA能通过病毒或其他感染因子在一个种群的不同个体中水平扩散,速度将会更快,应当记住,尽管这种“感染”肯定要影响整个生殖细胞系而不是仅仅影响体细胞。如果这种初始扩增在产生的冗余DNA数量相对较小时发生,则不太可能受到生物体选择对其的严重阻碍。对于这些过程的研究显然需要一种新型的种群遗传学。 英文
自私DNA能获得一种特异性功能吗?
如果宿主生物没能偶然地发现特定自... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 这种现象说明,影响减数分裂时间的是有用DNA与垃圾DNA的比值,而不是全部DNA的含量。 英文
在美国的某种蝾螈中也可以发现类似的情况。它们的发育和生长周期的速率往往相差很大,热带品种通常比温带品种需要更长的生长发育时间。戴维·韦克博士和赫伯特·麦格雷戈博士(个人交流)告诉我们,有初步证据显示发育期较长的物种通常具有较高的C值。这个结论与前面描述的草本植物的情况相类似。是否有更进一步的证据来继续支持这个推断,还要拭目以待。(请参阅厄尔德费等[25]关于25种蛙类的有趣文章。他们得出结论“基因组的大小为发育设置了上限,导致其不能加速发育。”) 英文
检验此学说
自私DNA的学说并没有模糊到不可检验。我们可以想到三种普适的检验方法。首先... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | In two review articles in the 17 April issue Doolittle and Sapienza (p. 601) and Orgel and Crick (p. 604) separately suggested that much of the DNA in the genome of higher organisms could be described as “selfish”. They argued that such DNA has no appreciable phenotypic effect and functions only to ensure its own self-... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | such as a change in the local rate of recombination. In some cases close similarity of two sequences may be important, while the base sequences themselves may matter hardly at all—for example, within the introns of two neighbouring versions of a gene. The word “junk” is perhaps too broad to cover all those cases for wh... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | There is obviously a continuum of possible selective advantages (positive or negative) to the organism. We had excluded from our definition of selfish DNA those cases where the selective advantage is very high. To decide whether a repeated sequence is parasitic or not, one must determine whether the presence of the rep... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | We proposed2 that the amount of non-specific DNA present in a given genome is often determined by the balance between the intragenomic spreading of selfish sequences and phenotypic selection against excess DNA—the weaker the phenotypic selection against non-specific DNA the larger the DNA content of the genome. In anot... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | needed to unravel the complexities of the situation. In particular, we should like to know in which stages and in which organisms the surface of the nuclear membrane is saturated with nuclear pores. 中文
Cavalier-Smith3 also cites the widely different DNA contents of germ cells and somatic cells in some invertebrates as ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | As for our own ideas, we now feel that there may perhaps be reasons why too little DNA can in some cases produce a selective disadvantage. For example, Zuckerkandel11 has suggested that there may be a minimum size for a “domain” necessary for stability of the chromatin in the folded state. Thus a domain containing only... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | In our recent experience most people will agree, after discussion, that ignorant DNA, parasitic DNA, symbiotic DNA (that is, parasitic DNA which has become useful to the organism) and “dead” DNA of one sort or another are all likely to be present in the chromosomes of higher organisms. Where people differ is in their e... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
在关于自私DNA的两篇综述里,对“自私的”、“垃圾”、“特异的”、“表型”这些词的使用引起了一些麻烦[1,2]。 英文
许多人不喜欢“自私DNA”这个术语,而更倾向于接受“寄生DNA”这一替代词语。尽管某些病毒的DNA可以在个体之间移动,但是“寄生”这一词语并不意味着DNA可以在个体之间转移。不过这个词语的确暗示这种DNA可以在同一细胞的不同染色体间发生移动。 英文
“垃圾”一词似乎也具有强烈的感情色彩。其隐藏的含意可以通过考虑“特异”这一含义而得以阐明。如果一条序列任意一个碱基的变化几乎都会对生物产生明显影响的话,我们就将其视为一条高度特异性的序列,例如一个与生理相关的限制性内切酶的识别位点。另一个极端是有些序列的缺失或广泛... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 如果核膜面积由细胞核的DNA含量决定,那么就会遵循如下原则,即自然选择倾向于大细胞,这必然导致基因组DNA含量的增加。因此,令人非常惊讶的是,冗余的非特异DNA由于其允许这种细胞生长得更快而被选择。尽管我们不会质疑这个论点的逻辑性,但考虑到多方面的假设,我们发现并不是所有的假设都是特别可信的。有时环境可能会选择增大的细胞体积和增大的细胞核体积,在这样选择出来的细胞中,非特异性DNA能够积累下来。上述行为的原因,可能是具有大细胞核的大细胞需要这种累积,或者细胞只是简单地允许其能够存在而最终被观察到。我们认为有必要做更多的实验来揭开这一情况的复杂性。尤其我们想知道在哪个阶段以及在何种生物体内核膜表面的核孔能够达到饱和。 英文
卡弗利尔-... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Modes of Genome Evolution
G. Dover and W. F. Doolittle
Editor’s Note
Following on from the previous addendum to two pieces on “selfish DNA” published in April of this year, here the author of one of those pieces, biochemist Ford Doolittle, collaborates with one of his critics, geneticist Gabriel Dover at Cambridge Univ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | sequence rearrangement and the behaviour of elements which promote their own amplification and dispersion will of course depend on the effects they have on fitness. Hence, the net accumulation of these particular families of sequences reflects a balance between the intrinsic rate of accumulation (intra-genomically) and... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | self-perpetuation of sequences initially chosen at random13 and also that amplification and dispersion can be part and parcel of the same recombinational irregularity14. 中文
A process of recurrent amplification can explain the frequent observation of a greater within-species than between-species sequence homogeneity of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | We do not agree upon the relative contributions of randomly accumulated and preferentially accumulated DNAs to the evolution of eukaryote genomes. It is clear that much of the non-coding DNA of yeast could be of the sort one could call “selfish”4,8 whilst non-coding elements of the D. melanogaster genome are made up of... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | We do not know what proportions of the repetitive DNAs of “higher” organisms are amplified and dispersed by either sequence-dependent or sequence-independent mechanisms. Similarly, we do not know to what extent each of these mechanisms is constrained nor do we know the extent to which the frequencies of sequence patter... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Brutlag, E. E. et al. Cold Spring Harb. Symp. Quant. Biol. 42, 1137 (1979).
Wensink, P. C. et al. Cell 18, 1231 (1977).
Jelinek, W. R. et al. Proc. Natl. Acad. Sci. U.S.A. 77, 1398 (1980).
Rubin, C. M. et al. Nature 284, 372 (1980).
Bell, G. L. et al. Nucleic Acids Res. 8, 4091 (1980).
基因组的进化模式
多弗,杜利特尔
编者按
上一篇文章是当年四月发... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 以黑腹果蝇的偏分离(SD)为例,SD染色体的优先恢复并不完全取决于它的积累本身,而是携带非SD同源物的细胞发育不良的结果[22]。这种情况及其他情况类似于等位基因在一个基因位点上频率的相对改变,这种改变也是自然选择的结果。“自私的”和“复制子选择”都是对等位基因和染色体的这种差异性积累过程的误导性描述。 英文
我们并不认同随机积累和优先积累的DNA对真核基因组进化的相关贡献。很明显,酵母的很多非编码DNA都可能是被称为“自私的”的类型[4,8];而黑腹果蝇基因组的非编码元件则是由不同比例的本质上“未知的”重复DNA(例如卫星DNA[23])和“无意识的”转座DNA(例如“copia样”元件[5])组成。温辛克和他的同事们[24]在黑... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | In systematic searches for embryonic lethal mutants of Drosophila melanogaster we have identified 15 loci which when mutated alter the segmental pattern of the larva. These loci probably represent the majority of such genes in Drosophila. The phenotypes of the mutant embryos indicate that the process of segmentation in... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | segments is thought to occur by a differential response of the zygotic genome to the maternal gradient. Homeotic mutations (for example, bithorax5,6) seem to be involved in a final step of this response process. These mutations change the identity of individual segments; for example, Ultrabithorax transforms the metath... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | † The numbers in parentheses refer to the alleles listed in Lindsley and Grell20. All other alleles, except the runt allele, three Kr alleles and one knirps allele, were isolated in screen for embryonic lethal mutants on the second chromosome. 5,800 balanced stocks were established from individual males heterozygous fo... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 3. The patterns of fused and ciD (not shown) look similar to the gooseberry pattern, whereas in hedgehog and wingless the deleted regions are somewhat larger, cutting into the denticle bands at either side. Four pair-rule mutants are shown in the centre. The interpretation of their phenotypes is based on the study... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 2. Ventral cuticular pattern of (from left to right) a normal Drosophila larva shortly after hatching, and larvae homozygous for gooseberry, hedgehog and patch. The mutant larvae were taken out of the egg case before fixation. All larvae were fixed, cleared and mounted as described in ref. 22. A, abdominal segment... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | large and pigmented whereas those of the thorax are short and pale (Figs 1, 2). The anterior margin of the region duplicated in these mutants coincides with the segment boundary in only two cases, fused and gooseberry (Fig. 3). In wingless and hedgehog it lies posterior to the boundary, such that these larvae apparentl... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | posterior second abdominal segment, etc. The identification of the regions present or deleted in mutant larvae is based on the phenotypes produced by alleles with lower expressivity. In such embryos the deletions are in general smaller and variable in size. In a “leaky” allele of even-skipped, the denticle bands of the... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | within the segmental array rather than the segmental identity. These combinations thus provide evidence that mutations such as paired and even-skipped affect different processes from those altered in homeotic mutants. 中文
Other mutants in this class show different deletion patterns. The phenotype of odd-skipped is simil... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | One of the striking features of the mutations of the first two classes is that the alteration in the pattern is repeated at specific intervals along the antero-posterior axis of the embryo. No such repeated pattern is found in mutants of the third class and instead a single group of up to eight adjacent segments is del... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | identity. 中文
All three loci are required for a normal segmental subdivision of one continuous body region. The lack of a repeated pattern of defects suggests that the loci are involved in processes in which position along the antero-posterior axis of the embryo is defined by unique values. 中文
When Are Genes Affecting S... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Segmentation in Drosophila proceeds by the transition from a single field into a repeated pattern of homologous smaller subfields. Mutant alleles at the 15 loci we have described interfere with this process at various points. Although each locus has its own distinct phenotype, we were able to distribute the mutations i... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The smallest repeat unit, the individual segment, is affected in mutants at the six segment-polarity loci. The pattern alteration consists of a mirror-image duplication of part of the normal pattern with the remainder deleted. In these mutants the deleted region corresponds in size to more than half a segment. Mutation... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | establishment of segment boundaries every three to four cells. A stepwise establishment of segments implies that the borders defining double segments be made before the intervening ones. The mutant phenotypes do not definitely show which, if any, of the segment borders define a primary double segmental division in norm... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | embryonic lethal loci). From this yield and similar calculations for the third and first chromosomes, we estimate that we have identified almost all segmentation loci on the second chromosome and about 50% each of those on the third and first chromosome. Our sample of 15 loci should therefore represent the majority of ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Counce, S. Z. Induktive Abstammungs-Vererbungslehre 87, 462–81 (1958).
Sharma, R. P. & Chopra, V. L. Devl. Biol. 48, 461–465 (1976).
Lawrence, P. A. & Morata, G. Devl. Biol. 50, 321–337 (1976).
Kornberg, T., in preparation.
Gloor, H. Arch. Julius-Klaus-Stift. VererbForsch, 25, 38–44 (1950).
Meinhardt, H. J. Cell Sci. 2... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 本文我们描述的突变体涉及15个基因座,每个突变体表现出以下三种新型模式改变中的某一种:每个体节都存在重复模式(体节极性突变体;6个基因座)、体节交替缺失(成对控制突变体;6个基因座)和一组邻近体节缺失(间隙突变体;3个基因座)(表1,图1)。 英文
表1. 影响果蝇体节形成的基因座
* 对于新的基因座(见上表),图谱定位基于二号染色体的S,Sp,Bl,cn和bw标记之间的重组以及三号染色体上ru,h,th,st,cu,es及ca标记之间的重组。对标记的描述见参考文献20。运用各自区域的缺失和复制断点,对“侏儒”、“跛子”和“折叠扇”基因座进行了进一步定位。所有突变都是通过计算重单重组体雄性与来自最初突变体品系的杂合体雌性回交后产生... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 这一类型的所有突变都是纯合致死的,并且突变表型只在纯合胚胎中产生。其中“融合”这个基因座还具有母体效应,因为母体中一个野生型等位基因足以挽救其纯合胚胎的突变体表型。 英文
除“斑点”外,所有突变体的缺失部分都包括体节模式中裸露的后部区域,而其重复部分则都包含前部齿状带的大块区域。突变幼虫每个体节的腹侧都几乎完全被小齿覆盖,小齿后部指向前部。体节特性似乎正常,腹节的小齿大且色素化而胸节的小齿短且颜色淡(图1和2)。只有在“融合”和“鹅莓”这两种突变体中重复部分的前缘才与体节边界一致(图3)。在“无翅”和“刺猬”突变体中,重复部分的前缘位于体节边界之后,以至于这些幼虫明显缺少了所有体节边界。 英文
“斑点”纯合突变胚胎重复区域的每个齿状... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
间隙突变体:一组连续体节缺失
前两类突变的一个显著特征是,沿着胚胎的前后轴模式的改变以特定的间隔重复出现。在第三类突变中不存在这种重复特性,取而代之的是在最终模式中最多连续八个相邻体节一起缺失。已经鉴定出三个引起这类间隙突变的基因座(表1,图1和5)。“跛子”(Kr)突变最早是由格洛尔描述的[12]。“跛子”纯合胚胎没有胸部和前腹部。尾部末端及第八、七、六腹节正常,但是有些许变大。在第六腹节的前面是一个镜像对称的平面,该平面连着另一个具有第六体节特征但极性相反的体节带。对称平面的精确位置是变化的,通常不与体节边界一致。“跛子”突变的大部分模式都使人联想到母体效应“双尾”突变体产生的胚胎模式,虽然母体成分并未参与“跛子”表型的产... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 最初分化为双体节可避免每三到四个细胞同时形成各体节边界时所遇到的准确性问题。体节的逐步形成意味着双体节边界是在中间边界之前形成的。突变体表型并未确切地显示确立正常发育中的双体节分区的体节边界。如果从双体节到单体节的转变过程被打断,与预期模式最接近的突变表型是“配对”和“偶数–遗漏”突变的表型。两者都提示中胸和后胸,第一、第二、第三和第四腹节等结构。 英文
也可能双体节单位在正常发育中从未被明显的边界所划分。双体节同源单位的存在可能仅仅反映了一种连续性质,就像一种以双体节为周期的波,这种波与体节边界的正确划分有关(举例说明可以见参考文献18,19)。我们未发现重复单位大于两个体节的突变体。这可能说明了胚盘直接通过没有更大的中间同源单位... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Pluripotential cells are present in a mouse embryo until at least an early post-implantation stage, as shown by their ability to take part in the formation of chimaeric animals1 and to form teratocarcinomas2. Until now it has not been possible to establish progressively growing cultures of these cells in vitro, and cel... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | stage seem to be the best candidates for direct progenitors of pluripotential cells in culture. As these embryos are difficult to isolate, and as the cell number in the isolated epiblast is small, we chose an alternative route to obtain embryo cells at this stage of development. 中文
Mouse blastocysts may be induced to e... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | colonies of cells closely resembling EC cells were apparent from an early stage. These colonies were picked out, passaged and mass cultures grown. The cell cultures had the appearance and general growth characteristics of feeder-dependent EC cells (Fig. 1). 中文
Fig. 1. Groups of pluripotential embryo cells (arrowed) gr... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Fig. 2. Karyotype of an embryo-derived pluripotential cell line, 40XY. Over 80% of the spreads of this clonal line possessed 40 chromosomes and had a clearly identifiable Y chromosome.
中文
Cultures of EK cells were collected by trypsinization, and ~106 cells injected subcutaneously into the flank of syngeneic male mic... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | g, transfer of embryonal carcinoma cells either from cell culture or from the core of an embryoid body or from a solid tumour back to a blastocyst. All these procedures may result in chimaerism of the resulting mouse; h, the missing link supplied here.
中文
Teratocarcinoma cells are now being widely used as a model for... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Atienza-Samols, S. B. & Sherman, M. I. Devl. Biol. 66, 220-231 (1978).
Solter, D. & Knowles, B. Proc. Natl. Acad. Sci. U.S.A. 72, 5099-5102 (1975).
Evans, M. J. J. Reprod. Fert. 62, 625-631 (1981).
Evans, M. J., Lovell-Badge, R. H., Stern, P. L. & Stinnakre, M. -G. INSERM Symp. 10, 115-129 (1979).
McLaren, A. J. Endocr... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 将近似卵筒结构挑出培养皿,用胰蛋白酶处理使其分散,并在明胶预处理的含有丝裂霉素C灭活的STO成纤维细胞的培养皿中进行传代。所有的培养都使用杜尔贝科改良的最低必需培养基加上10%的胎牛血清和10%的新生牛血清。每天检查培养物,每2~3天用胰蛋白酶消化进行传代培养。从早期阶段开始,非常类似于EC细胞的活跃增殖的细胞集落就很明显了。将这些集落挑出、传代并大规模培养。这些细胞培养物具备饲养层依赖的EC细胞的外观和一般生长特征(图1)。 英文
图1. 在丝裂霉素C抑制的STO细胞背景中,呈单层生长的多能胚胎细胞群(箭头)。只需要大约3周就可从囊胚中分离到一种特定的细胞系,而且在传代5天之内就能观察到多能细胞集落。在一次实验中,我们已经从囊胚... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
(毛晨晖 翻译;梁前进 审稿)
Test-tube Babies, 1981
R. G. Edwards
Editor’s Note
Robert Edwards, in collaboration with Patrick Steptoe in England, enabled the first birth of a baby by in vitro fertilization (IVF), Louise Brown, in 1978. Their research had been considered controversial, and the birth was met with a mixture of sur... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Harvesting preovulatory oocytes is the first of several steps essential for obtaining human embryos. They must be collected during their final stages of maturation just before ovulation occurs, when meiosis is advanced and cortical granules have established the defence against polyspermy. Follicular growth and ovulatio... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | pituitary gland of such patients over several days, so preventing the LH surge in response to rising levels of oestrogens. HCG must be given at some arbitrary time, before follicles become atretic, yet while it is uncertain if the patient will have her own endogenous LH surge. Ovarian stimulation can also distort the m... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | and for oestrogens. Fortunately, the LH surge begins in early morning in almost three-quarters of the women (Fig. 2), which is most convenient for the collection of preovulatory oocytes 24-28 h later. This “critical period” in the LH surge in women resembles the situation in rats16,17, and its distinct diurnal componen... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | of oocytes, and preliminary laparoscopy may be required to alleviate these conditions. If the ovary is accessible, oocytes can be collected during the natural cycle from almost 90% of patients, laparoscopy being completed within a few minutes (Table 1). None of our patients had ovulated when laparoscopy was performed, ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | medium under oil, adding 1.5-2×105 living spermatozoa per ml between 3 and 4 h after aspiration of oocytes; the oocytes are placed in tubes some hours later when most of their cumulus cells have been shed12. 中文
Table 2. Fertilization of human eggs in vitro
* Recent survey of 122 patients (See Table 1).
中文
Table 3. C... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Implantation is the most difficult and unpredictable stage. In animals, rates of implantation are high when embryos are replaced surgically (>70%), but lower if replaced non-surgically via the cervix (~50%)28,29. Almost all human embryos have been replaced transcervically, and approximately one-quarter of them have imp... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Physiological disorders might prevent implantation. Vaginal distension during replacement could invoke discharges of prolactin, and a catheter passed through the uterine cavity may invoke a premature decidualization of the endometrium. Slight myometrial contractions could expel embryos soon after their replacement and ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | cleavage errors in the embryo35. Nor should trisomy be more frequent after fertilization in vitro. Most human trisomies arise during the first meiotic division of the oocyte36,37, a stage which is virtually complete before the oocytes are aspirated. Others arise during the second meiotic division, that is, after fertil... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | The thought of cloned human embryos identical to a pre-existing individual is not attractive. Yet, in a sense, uniparental human embryos largely similar to the father already exist. Hydatidiform moles are the remains of diploid androgenetic fetuses, in which the trophoblast proliferates over several weeks to form large... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Many children will soon be born after the fertilization of human eggs in vitro. We have established more than 40 pregnancies since resuming work during the past 9 months, and the majority are surviving. This is most encouraging for those couples who could not be offered any other form of corrective surgery and have so ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Trounson, A. O. et al. 3rd World Congress of Human Reproduction, Berlin (Excerpta Medica, Amsterdam, 1981).
Fowler, R. E., Edwards, R. G., Walters, D. E., Chan, S. T. H. & Steptoe, P. C. J. Endocr. 77, 161 (1978).
Baudendistel, L. J., Ruh, M. F., Nadel, E. M. & Ruh, T. S. Acta Endocr. 89, 599 (1978).
Katzellenbogen, B.... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | Rowson, L. E. A. (ed.) Egg Transfer in Cattle (Commission of European Communities, Brussels, 1976).
Sreenan, J. N. Theriogenology, 9, 69 (1978).
Lundström, V., Eneroth, P., Granström, E. & Swahn, K.-L. 3rd World Congress of Human Reproduction, Berlin (Excerpta Medica, Amsterdam, 1981).
Akerjund, M., Andersson, K.-E. & ... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 很多关键步骤目前都有很高的成功率,包括排卵期前的卵母细胞的收集以及体外的受精及胚胎卵裂。主要的困难仍然在于胚胎移入母体后的着床。本文还对这项研究的一些应用进行了讨论。 英文
这一年应该是通过人类卵细胞体外受精诞生婴儿的转折点。在英国和澳大利亚,将有15到20名婴儿通过这种方式来到人世,两个国家的数目相近,其他国家也有1~2名。很多国家会引入这种技术,主要用于减轻人类不育症。影响人类怀孕的基本因素将得到分析,而且针对基因工程的争论想必也将越来越多。因此,是时候来评价这项技术带来的相关临床和科学问题了[1]。 英文
第一项要素:排卵时间
首先我将讨论计算排卵时间以便收集排卵期前的卵母细胞的方法。 英文
获得人类胚胎的几个关键步骤中首要步... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 英文
卵母细胞的吸取
使用双腔吸引管或者两根单独的针管,一个用于吸取细胞,另一个用于在没有采集到卵母细胞时冲洗掉卵泡[19,20]。冲洗液可以含有肝素,可以防止卵泡内凝血。 英文
采集成功率最高的时间是在HCG注射后的第32小时,或者在尿液中LH含量升高后的第26小时(表1)。准确计算排卵起始的时间是非常重要的。如果在内源性LH峰后注射HCG,开始吸取卵母细胞之前排卵就可能发生。紧张性LH释放的昼夜节律性有时会在数小时内达到较低的峰值,而混淆了LH达峰的准确时间(图3)。盆腔粘连、输卵管积水、囊状卵泡、子宫内膜异位以及其他卵巢疾病都会影响卵细胞的采集,可能需要用腹腔镜预处理以减轻这些症状。如果卵巢可直接到达的话,几乎90%的患者都可... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | † 这些患者在黄体期的第7天或者第8天体内孕酮的浓度是0.4 ng/ml到2.7 ng/ml之间。
‡ 一些其他患者表现出了月经复潮的延迟,但是没有发现HCGβ或者HCG/LH升高的证据。
英文
为什么只有少数胚胎能着床?或许预期着床成功的几率只有20%左右,这个数据类似于数个调查中所报告的人类自然生育率。这个观点似乎有些悲观。如果导管进入宫颈内口遇到困难,那么有些胚胎可能丢失或者被感染。这种情况下使用外层金属套管是有帮助的,但是怀孕率更低(表4)。带有光滑尖端和侧孔的特氟龙导管明显很容易通过宫颈内口[6],但是可能需要在宫颈内使用宫颈钳。从二细胞到囊胚期的各个阶段的胚胎都能够着床,但是没有充足的数据说明哪个阶段是移植的最佳时期[... | 400套付费套装书 |
C:\Users\yuan\Documents\400套付费套装书\04-100套\epub\0304. 《自然》百年科学经典(英汉对照版)(第六卷)(1973-1984).epub | .epub | 45,637,976 | 2025-09-26T19:07:36.672222 | 显然,有关这种治疗方法在预防遗传性疾病比如糖尿病的基因表达方面的潜在价值还没有相关知识。 英文
展望
越来越多的婴儿将会通过人卵细胞体外受精的方式诞生。自恢复体外受精的研究后,在过去的9个月内我们已经为40多位患者建立妊娠,且绝大多数胎儿仍然存活。对于那些无法获得其他任何形式的矫正手术以及目前为止没有得到有效治疗的夫妇来说,这是非常令人鼓舞的(表5)。这种方法在同一个患者身上可以进行多次,很快成功率将超过一些其他类型的输卵管手术。如果使用卵巢刺激,“多余的胚胎”还可以用于胚胎学研究,其中一个胚胎在体外一直成长了9天直到第5a阶段(参考文献3)。人类胚胎的冷冻储存似乎还很遥远。一些少精父亲、先天性不育患者(尚不能解释原因的)和宫颈黏液... | 400套付费套装书 |
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