Rodionov A V
Biological Research Institute, St. Petersburg State University, Russia.
Genetika. 1999 Mar;35(2):277-90.
Specific chromosome banding patterns in different eukaryotic taxons are reviewed. In all eukaryotes, chromosomes are composed of alternating bands, each differing from the adjacent material by the molecular composition and structural characteristics. In minute chromosomes of fungi and Protozoa, these bands are represented by kinetochores (Kt- (Cd-)bands), nucleolus organizers (N-bands), and telomeres as well as the euchromatin. In genomes of most fungi and protists, long clusters of tandem repeats and, consequently, C-bands were not revealed but they are likely to be found out in species with chromosomes visible under a light microscope, which are several tens of million bp in size. Chromosomes of Metazoa are usually larger. Even in Cnidaria, they contain C-bands, which are replicated late in the S phase. In Deuterostomia, chromosome euchromatin regions differ by replication time: bands replicating at the first half of the S phase alternate with bands replicating at the second half of the S phase. Longitudinal differentiation in the replication pattern of euchromatic regions is observed in all classes of Vertebrata beginning with the bony fish although the time when it developed in Deuterostomia is unknown. Apparently, the evolution of early and late replicating subdomains in Vertebrata euchromatin promoted fast accumulation of differences in the molecular composition of nucleoproteid complexes characteristic of early and late replicating bands. As a result, the more contrasting G/R and Q-banding patterns of chromosomes developed especially in Eutheria. The evolution of Protostomia and Plantae followed another path. An increase in chromosome size was not accompanied by the appearance of wide RBE and RBL euchromatin bands. The G/R-like banding within the interstitial chromosome regions observed in some representatives of Invertebrates and higher plants arose independently in different phylogenetic lineages. This banding pattern seems to be closer to that of C-banding than to the typical G/R-banding of the mammalian chromosomes.
本文综述了不同真核生物分类群中特定的染色体带型。在所有真核生物中，染色体由交替的带组成，每条带在分子组成和结构特征上与相邻物质不同。在真菌和原生动物的微小染色体中，这些带由着丝粒（Kt-（Cd-）带）、核仁组织区（N-带）、端粒以及常染色质代表。在大多数真菌和原生生物的基因组中，未发现串联重复序列的长簇以及因此的C-带，但在染色体大小为数千万碱基对、在光学显微镜下可见的物种中可能会发现它们。后生动物的染色体通常较大。即使在刺胞动物门中，它们也含有在S期后期复制的C-带。在后口动物中，染色体常染色质区域在复制时间上有所不同：在S期前半段复制的带与在S期后半段复制的带交替出现。从硬骨鱼开始，在所有脊椎动物类群中都观察到常染色质区域复制模式的纵向分化，尽管在后口动物中其出现时间尚不清楚。显然，脊椎动物常染色质中早期和晚期复制亚结构域的进化促进了早期和晚期复制带特征性的核蛋白复合物分子组成差异的快速积累。结果，特别是在真兽亚纲中，染色体的G/R和Q带型差异更大。原口动物和植物的进化遵循另一条路径。染色体大小的增加并未伴随着宽的RBE和RBL常染色质带的出现。在一些无脊椎动物和高等植物的代表中观察到的间质染色体区域内类似G/R的带型在不同的系统发育谱系中独立出现。这种带型似乎比哺乳动物染色体的典型G/R带型更接近C带型。
