注册 登录  
 加关注
   显示下一条  |  关闭
温馨提示!由于新浪微博认证机制调整,您的新浪微博帐号绑定已过期,请重新绑定!立即重新绑定新浪微博》  |  关闭

蒋世禄的生物课堂内外

教师要做到专业性和终身性,目标是研究型教师。——互动平台欢迎您!

 
 
 

日志

 
 

【转载】赫尔希和蔡斯论证蛋白质很可能不是遗传物质  

2013-01-12 08:09:10|  分类: 教材研究探讨 |  标签: |举报 |字号 订阅

  下载LOFTER 我的照片书  |
先把原文的摘要翻译一下。(水平有限,望读者不吝指出错误。但我自信能大体反映作者的思路。蓝字部分为我的评论。)

INDEPENDENT FUNCTIONS OF VIRAL PROTEIN AND NUCLEIC ACID IN GROWTH OF BACTERIOPHAGE
蛋白质和核酸在噬菌体繁殖中的独立功能
按:感情人教版教材所说的“把蛋白质和DNA分开,单独的观察各自的作用”来自于此。

1. Osmotic shock disrupts particles of phage T2 into material containing nearly all the phage sulfur in a form precipitable by antiphage serum, and capable of specific adsorption to bacteria. It releases into solution nearly all the phage DNA in a form not precipitable by antiserum and not adsorbable to bacteria. The sulfur-containing protein of the phage particle evidently makes up a membrane that protects the phage DNA from DNase, comprises the sole or principal antigenic material, and is responsible for attachment of the virus to bacteria.
渗透震荡裂解T2噬菌体颗粒。噬菌体的含硫成分几乎全部可以在抗噬菌体血清中沉淀而且可以吸附到细菌上。几乎所有的噬菌体DNA都释放到溶液中,不能被抗噬菌体血清沉淀,不能吸附到细菌上。噬菌体颗粒的含硫蛋白显然构建了防止DNA被DNA酶分解的膜,包含了全部或主要抗原物质,并且负责把病毒粘附到细菌上。

2. Adsorption of T2 to heat-killed bacteria, and heating or alternate freezing and thawing of infected cells, sensitize the DNA of the adsorbed phage to DNase. These treatments have little or no sensitizing effect on unadsorbed phage. Neither heating nor freezing and thawing releases the phage DNA from infected cells, although other cell constituents can be extracted by these methods. These facts suggest that the phage DNA forms part of an organized intracellular structure throughout the period of phage growth.
把T2噬菌体吸附到加热杀死的病菌上,加热或反复冰冻与解冻感染的细胞,使吸附的噬菌体DNA对DNA酶敏感。这些处理没有或很少影响没有吸附的噬菌体。不论加热还是冰冻解冻都不能从感染细胞中释放出噬菌体DNA。当然,这些方法可使其他细胞组分从细胞中提取出来。这些事实暗示,在噬菌体的生长周期中,噬菌体的DNA构建了部分细胞内的有序结构。

3. Adsorption of phage T2 to bacterial debris causes part of the phage DNA to appear in solution, leaving the phage sulfur attached to the debris. Another part of the phage DNA, corresponding roughly to the remaining half of the DNA of the inactivated phage, remains attached to the debris but can be separated from it by DNase. Phage T4 behaves similarly, although the two phages can be shown to attach to different combining sites. The inactivation of phage by bacterial debris is evidently accompanied by the rupture of the viral membrane.
T2噬菌体吸附到细菌碎片导致部分噬菌体DNA出现在溶液中,噬菌体的含硫部分则一直粘附在细菌碎片上。另外一部分噬菌体DNA(大约相当于失活噬菌体DNA的一半)一直粘附在碎片上,但能够用DNA酶分离。T4噬菌体有相似的情况,只是两种噬菌体看上去粘附在不同的结合位点。这种噬菌体的失活显然伴随着病毒外壳的破裂。

4. Suspensions of infected cells agitated in a Waring blendor release 75 per cent of the phage sulfur and only 15 per cent of the phage phosphorus to the solution as a result of the applied shearing force. The cells remain capable of yielding phage progeny.
侵染细胞悬浮液用华林绞切机搅拌,在特定搅拌力的作用下释放到溶液中的噬菌体硫占75%噬菌体磷只占15%。细胞仍然保留着产生子代噬菌体的能力。

5. The facts stated show that most of the phage sulfur remains at the cell surface and most of the phage DNA enters the cell on infection. Whether sulfur-free material other than DNA enters the cell has not been determined. The properties of the sulfur-containing residue identify it as essentially unchanged membranes of the phage particles. All types of evidence show that the passage of phage DNA into the cell occurs in non-nutrient medium under conditions in which other known steps in viral growth do not occur.
事实明确的显示出,侵染过程中,多数的噬菌体硫保留在细胞表面,而多数的噬菌体DNA进入了细胞。DNA以外的无硫物质是否进入细胞无法确定。含硫残渣的性质鉴定表面,它与噬菌体颗粒的外壳性质一致。各种证据显示,在其他已知的病毒繁殖步骤尚未发生的条件下,在无营养的介质中,DNA进入细胞的过程已经发生。

6. The phage progeny yielded by bacteria infected with phage labeled with radioactive sulfur contain less than 1 per cent of the parental radioactivity. The progeny of phage particles labeled with radioactive phosphorus contain 30 per cent or more of the parental phosphorus.
用放射性硫标记的噬菌体侵染细菌产生的噬菌体后代中存在不到1%的亲代放射性物质。用放射性磷标记的噬菌体颗粒后代含有30%或更多的亲代磷。

7. Phage inactivated by dilute formaldehyde is capable of adsorbing to bacteria, but does not release its DNA to the cell. This shows that the interaction between phage and bacterium resulting in release of the phage DNA from its protective membrane depends on labile components of the phage particle. By contrast, the components of the bacterium essential to this interaction are remarkably stable. The nature of the interaction is otherwise unknown.
用甲醛处理失活的噬菌体不能吸附细菌,也不释放其DNA到细胞中。这显示出,导致噬菌体DNA从保护壳内释放出来的噬菌体和细菌的相互作用依赖于噬菌体颗粒中不稳定的成分。相反,细菌中此相互作用所必需的物质却出乎意料的稳定。这种相互作用的本质尚不明确。

8. The sulfur-containing protein of resting phage particles is confined to a protective coat that is responsible for the adsorption to bacteria, and functions as an instrument for the injection of the phage DNA into the cell. This protein probably has no function in the growth of intracellular phage. The DNA has some function. Further chemical inferences should not be drawn from the experiments presented.
休眠的噬菌体颗粒含硫蛋白质围成一个保护壳,负责吸附到细菌上,并且作为噬菌体DNA注射到细胞的装置。蛋白质可能对细胞中噬菌体的繁殖过程不起作用。DNA可能起了一些作用。无法从实验结果中得出更多的化学推论

按:看来即使赫尔希和蔡斯也认为该实验并不能完全证明DNA是遗传物质,也无法证明蛋白质不是遗传物质。但其原因并非如一些高中教辅所说的“需要将蛋白质注入细菌再观察其是否发挥遗传物质的作用”。其原因是:第一,不是所有的蛋白质都含有硫,此实验无法证明不含硫的蛋白质非遗传物质;第二,无法证明放射性的硫完全不进入细菌;第三,无法证明放射性的硫完全不传递给后代。但是根据实验结果看,蛋白质是遗传物质的可能性并不大,DNA在遗传中发挥作用的可能性更大。
  评论这张
 
阅读(319)| 评论(1)
推荐 转载

历史上的今天

在LOFTER的更多文章

评论

<#--最新日志,群博日志--> <#--推荐日志--> <#--引用记录--> <#--博主推荐--> <#--随机阅读--> <#--首页推荐--> <#--历史上的今天--> <#--被推荐日志--> <#--上一篇,下一篇--> <#-- 热度 --> <#-- 网易新闻广告 --> <#--右边模块结构--> <#--评论模块结构--> <#--引用模块结构--> <#--博主发起的投票-->
 
 
 
 
 
 
 
 
 
 
 
 
 
 

页脚

网易公司版权所有 ©1997-2017