Savage J R
MRC Radiobiology Unit, Chilton, Didcot, United Kingdom.
Environ Mol Mutagen. 1993;22(4):198-207. doi: 10.1002/em.2850220404.
The early radiobiologists, who developed target theory to explain their results, considered the chromosome "target" as a visible thread that could be physically broken by ionizing radiation. Most of the broken ends restituted, but those that did not were free to wander about and, within limits, could rejoin with any other broken end they happened to contact to form structural aberrations. Failing this, they could remain to be seen as "open" breaks at the subsequent metaphase. These ideas, and their inevitable consequences, still form the basis for much modern thinking, even though we now known that the structure of the chromosome, and of the interphase nucleus, are very much more complicated than the originators of the theory envisaged. Current understanding of chromosomes at the molecular level and the varied responses a cell can mobilize when damage is introduced, raise again the question, Can we still think in terms of simple targets? Some of the experimental observations and suggestions made since those early days are reviewed, and the application of target theory to the three theories of aberration origins (Classic, Exchange, Recombination) is briefly discussed.
早期的放射生物学家通过发展靶学说来解释他们的研究结果，他们将染色体“靶”视为一条可见的细丝，能够被电离辐射物理性地打断。大多数断裂末端会恢复原状，但那些未能恢复的末端则可以自由游走，并且在一定范围内，能够与它们偶然接触到的任何其他断裂末端重新连接，从而形成结构畸变。若无法实现这种重新连接，它们在随后的中期可能仍会表现为“开放”的断裂。这些观点及其必然的推论，至今仍是许多现代思考的基础，尽管我们现在知道染色体以及间期细胞核的结构比该理论的提出者所设想的要复杂得多。当前在分子水平上对染色体的理解以及细胞在受到损伤时能够调动的各种反应，再次引发了一个问题：我们是否仍然可以从简单靶标的角度进行思考？本文回顾了自早期以来的一些实验观察结果和建议，并简要讨论了靶学说在三种畸变起源理论（经典理论、交换理论、重组理论）中的应用。
