| Investigations of the chromosome aberration induced by ionization radiation have had decades of histories. A large number of studies show that analysis of the chromosome aberrations in survivals of radiation accident can be helpful to find out the aberration type and rate, the relation of radiation dosage and aberration rate . Otherwise, the chromosome break and rearrangement induced by radiation maybe play important pole in leading to the translocation and misalignment of cancer genes and other correlated genes. Although the true biological significance of break point regions has been not clear, there is no doubt that research on hot damage point is important part of study on after effect of radiation.The methods of analysis of the chromosome aberrations mainly include routine staining method,G-banding method and FISH technique .The routine staining method is based on the differences in the length of chromosome and the site of centromere to distinguish the aberration. G-banding method can recognize the minute changes in chromosome band pattern and precisely locate the break point. Because of these advantages over the routine staining method, it's the main means to identify chromosome inversion ,translocation and deletion in genetic diseases,haematological diseases,tumors and radiation damages. FISH technique can quickly analyze a number of cells making use of full chromosome probe to hybridize with sample. It is more sensitive and frequent in the recognition of translocation.Since the invention of AFM as a novel imaging technique in 1986, much progress has been made in the application of AFM to the imaging and the manipulation of biological structure .It doesn't require complex sample preparation such as fixing and staining and may be operated in a gaseous or aqueous environment. It can observe the dynamic process in real time and provide ultra-high resolution 3-D imaging. These features make AFM become an attractive technique to study the structure and the karyotyping of chromosome. In addition, AFM can dissect chromosome and obtain small DNA probes as a new micromanipulating tool. However, so far in only one report abroad, AFM was employed to analyze ionization radiation induced chromosome aberration. In that report Murakami et al using AFM' height data, chromatid gaps and chromatid breaks could be distinguished. The fibrous structure could be observed inside the break points region. These indicate that AFM is a useful tool for analysis of chromosome aberration induced by ionization radiation.To explore the potentiality of the atomic force microscopy in analysis of chromosome aberration and observation of structure, in this experiment AFM was applied to analyze the chromosome aberrations in five survivals of Shanghai "6·25" radiation accident on the basis of common techniques. AFM also provides a way for further study on mechanisms of radiation damage and carcinogenesis in genomic level.First, the chromosome stable aberrations in five survivals were determined by G-banding method and FISH technique. Then chosing the normal G-banded chromosomes, AFM as a new way was established to analyze aberrations. On the basis of these work, AFM was used to analyze the translocations occurring frequently and observe the structures of hot damage point. The results were compared with the optical microscopy finally.The analysis of aberrations in five survivals showed that the translocation aberrations occurred on the chromosome 1 most frequently and the frequencies maintained relative constant. Furthermore, AFM was successfully used to image the surface topography of normal chromosome and observe the banding patterns. The analysis of aberrations on the chromosome 1 by AFM suggested that this method not only identified the exact position of break point, but also imaged the three-dimension structure of hot damage point at high resolution. In conclusion, compared with the optical microscopy, AFM can obtain the more information for study of chromosome aberration induced by radiation. It's pos...
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