Baldari C T, Amaldi F
Chromosoma. 1977 Jun 23;61(4):359-68. doi: 10.1007/BF00288619.
The interspersion period of repetitive and unique sequences was analyzed by two different methods, electron microscopy and agarose gel electrophoresis, for four Amphibian species with different nuclear DNA content, namely the Anura Xenopus laevis (3 pg DNA per haploid genome) and Bufo bufo (7 pg) and the Urodela Triturus cristatus (23 pg) and Necturus maculosus (52 pg). Within each of the two subclasses it has been found that interspecific differences, in DNA content, due to variations in the amount of repetitive sequences, do not involve variations in length of the interspersed repetitive sequences. They remain about 380 base pairs. Furthermore, the unique sequences length has been found to be shorter in Bufo (760 base pairs) than in Xenopus (1600) and in Necturus (880) than in Triturus (1340). A study of the interspersion period has shown that the great difference in DNA content between Anura and Urodela, which had been previously shown not to have involved changes in the relative amounts of the various sequence classes, does not involve changes in the interspersion period.
运用两种不同方法（电子显微镜和琼脂糖凝胶电泳），对四种核DNA含量不同的两栖动物的重复序列和单一序列的散布周期进行了分析，这四种两栖动物分别是无尾目非洲爪蟾（单倍体基因组DNA含量为3 pg）、蟾蜍（7 pg），有尾目意大利真螈（23 pg）和斑泥螈（52 pg）。在这两个亚纲的每一类动物中，都发现由于重复序列数量的变化而导致的DNA含量种间差异，并不涉及散布重复序列长度的变化。它们大约保持在380个碱基对。此外，还发现蟾蜍的单一序列长度（760个碱基对）比非洲爪蟾（1600个碱基对）短，斑泥螈（880个碱基对）比意大利真螈（1340个碱基对）短。对散布周期的研究表明，无尾目和有尾目之间DNA含量的巨大差异，此前已表明并不涉及各类序列相对数量的变化，也不涉及散布周期的变化。
