Scheer U, Franke W W, Trendelenburg M F, Spring H
J Cell Sci. 1976 Dec;22(3):503-19. doi: 10.1242/jcs.22.3.503.
The arrangement of transcriptional units in the loops of lampbrush chromosomes from oocyte nuclei of urodele amphibia and from primary nuclei of the green alga Acetabularia have been studied in the electron microscope using spread preparations. Loops with different patterns of arrangement of matrix units (i.e. to a first approximation, transcriptional units) can be distinguished: (i) loops consisting of one active transcriptional unit; (ii) loops containing one active transcriptional unit plus additional fibril-free, i.e. apparently untranscribed, intercepts that may include 'spacer' regions; (iii) loops containing two or more transcriptional units arranged in identical or changing polarities, with or without interspersed apparent spacer regions. Morphological details of the transcriptional complexes are described. The observations are not compatible with the concept that one loop reflects one and only one transcriptional unit but, rather, lead to a classification of loop types according to the arrangement of their transcriptional units. We propose that the lampbrush chromosome loop can represent a unit for the coordinate transcription of either one gene or a set of several (different) genes.
利用铺展标本，在电子显微镜下研究了有尾两栖类卵母细胞核和绿藻伞藻初级细胞核灯刷染色体环中转录单位的排列。可以区分出具有不同基质单位（即初步近似为转录单位）排列模式的环：（i）由一个活性转录单位组成的环；（ii）包含一个活性转录单位加上额外的无纤维区域（即明显未转录的区域）的环，这些区域可能包括“间隔”区；（iii）包含两个或更多以相同或变化极性排列的转录单位的环，有或没有穿插的明显间隔区。描述了转录复合体的形态学细节。这些观察结果与一个环只反映一个且唯一的转录单位这一概念不相符，而是根据转录单位的排列导致了环类型的分类。我们提出，灯刷染色体环可以代表一个用于一个基因或一组几个（不同）基因协同转录的单位。
