Popov L S, Mednikov B M
Mol Biol (Mosk). 1977 Mar-Apr;11(2):286-93.
Pyrimidine sequences of DNA from three fishes: shark, protopterus and perch have been studied. These data together with the evidence from the literature were used to support earlier conclusions that dipnoi and cartilagenous fishes should be distinguished as independent classes. The clustering index, beta, and the total molar percentage of long pyrimidine oligonucleotides (Z) containing greater than or equal to 8 nucleotides--a new parameter offered by us--have been used in comparative investigation of DNAs. The new parameter has permitted to obtain a higher resolution in the analysis of our own and literature data on DNA pyrimidine clusters in fishes. Investigation of pyrimidine clusters and of the base composition of individual isoplits of these clusters using statistical analysis showed that DNA from shark, protopterus, sturgeon and perch significantly differ by many features. Significant differences between these DNAs were found also in the base composition. Thus, new evidence for distinguishing cartilagenous fishes and dipnoi as independent classes have been received.
对三种鱼类（鲨鱼、非洲肺鱼和鲈鱼）的DNA嘧啶序列进行了研究。这些数据连同文献中的证据被用来支持早期的结论，即肉鳍鱼类和软骨鱼类应被区分为独立的纲。聚类指数β以及包含大于或等于8个核苷酸的长嘧啶寡核苷酸的总摩尔百分比（Z）——我们提出的一个新参数——已被用于DNA的比较研究。这个新参数使得我们在分析自己的以及文献中关于鱼类DNA嘧啶簇的数据时能够获得更高的分辨率。使用统计分析对嘧啶簇以及这些簇的各个等分体的碱基组成进行研究表明，鲨鱼、非洲肺鱼、鲟鱼和鲈鱼的DNA在许多特征上有显著差异。在碱基组成方面也发现了这些DNA之间的显著差异。因此，获得了将软骨鱼类和肉鳍鱼类区分为独立纲的新证据。
