洋葱染色体螺旋与放射环结构的电镜观察

染色体经DNA特异染色后，观察到其最高层次结构是螺旋的，而次级结构存在着放射环结构，即由直径为25～30nm的DNA纤丝放射状折叠排列成约250nm左右的染色单体丝；染色单体丝进一步螺旋形成中期染色体结构。这些观察结果和染色体的螺旋与放射环共存模型非常相似。这个模型应更接近于洋葱染色体真实结构。

Observation of Chromosome Structure in Allium Cepa Cells by Means of Electron Microscopy

NAMA-Ur is a specific DNA stain method that has been developed in recent years. In the Allium cepa cells only the chromatin or chromosomes are heavily stained, the other components are bleached. After the chromosomes are stained by NAMA-Ur, we have observed that the highest order structure of chromosomes is helical；while the secondary structure is radically folding. The DNA fibres with a diameter of 25～30nm have radically folded into chromatid fibres in a diameter of approximately 250nm. The above results present new evidence to support the radial loop and coils coexist mode of chromosome. This mode may more possibly accord with the real chromosome structure.