Poptsova Maria S, Larionov Sergei A, Ryadchenko Eugeny V, Rybalko Sergei D, Zakharov Ilya A, Loskutov Alexander
University of Connecticut, Storrs, Connecticut, United States of America.
PLoS One. 2009 Jul 28;4(7):e6396. doi: 10.1371/journal.pone.0006396.
Maps of 2D DNA walk of 671 examined chromosomes show composition complexity change from symmetrical half-turn in bacteria to pseudo-random trajectories in archaea, fungi and humans. In silico transformation of gene order and strand position returns most of the analyzed chromosomes to a symmetrical bacterial-like state with one transition point. The transformed chromosomal sequences also reveal remarkable segmental compositional symmetry between regions from different strands located equidistantly from the transition point. Despite extensive chromosome rearrangement the relation of gene numbers on opposite strands for chromosomes of different taxa varies in narrow limits around unity with Pearson coefficient r = 0.98. Similar relation is observed for total genes' length (r = 0.86) and cumulative GC (r = 0.95) and AT (r = 0.97) skews. This is also true for human coding sequences (CDS), which comprise only several percent of the entire chromosome length. We found that frequency distributions of the length of gene clusters, continuously located on the same strand, have close values for both strands. Eukaryotic gene distribution is believed to be non-random. Contribution of different subsystems to the noted symmetries and distributions, and evolutionary aspects of symmetry are discussed.
对671条经检测染色体的二维DNA步移图谱显示，其组成复杂性从细菌中的对称半圈变化为古细菌、真菌和人类中的伪随机轨迹。基因顺序和链位置的计算机模拟转换将大多数分析的染色体恢复到具有一个转换点的类似细菌的对称状态。转换后的染色体序列还揭示了来自不同链的区域之间显著的片段组成对称性，这些区域与转换点等距。尽管染色体发生了广泛重排，但不同分类群染色体相对链上的基因数量关系在接近1的狭窄范围内变化，皮尔逊系数r = 0.98。对于总基因长度（r = 0.86）以及累积GC（r = 0.95）和AT（r = 0.97）偏斜也观察到类似关系。对于仅占整个染色体长度百分之几的人类编码序列（CDS）也是如此。我们发现，连续位于同一条链上的基因簇长度的频率分布在两条链上具有相近的值。真核基因分布被认为是非随机的。讨论了不同子系统对上述对称性和分布的贡献以及对称性的进化方面。
