Schmid M, Steinlein C, Feichtinger W, Poot M
Department of Human Genetics, University of Würzburg, FRG.
Cytogenet Cell Genet. 1993;62(1):42-8. doi: 10.1159/000133442.
DNA flow cytophotometric measurements demonstrate that the quantity of nuclear DNA of the South American leptodactylid frog Pleurodema brachyops is 3.4 times greater than that of P. thaul. Nevertheless, the conventionally stained karyotypes of both species are nearly identical. In the metaphase chromosomes of P. brachyops, the chromatin has a distinctly higher degree of packaging than in those of P. thaul. C-banding reveals that almost 6 times the constitutive heterochromatin is present in the karyotype of P. brachyops than in the karyotype of P. thaul. Analysis of fluorescence banding patterns shows that the chromosomes of P. brachyops contain AT- and GC-rich heterochromatin, whereas the karyotype of P. thaul is devoid of brightly fluorescing heterochromatin. The substantial differences in the genome sizes of Pleurodema is explained by homogeneous, symmetrical changes in the amounts of all DNA sequence classes along all chromosomes, which preserved the ancestral morphology of the chromosomes.
DNA流式细胞光度测量表明，南美细趾蟾科蛙类短头侧褶蛙（Pleurodema brachyops）的核DNA数量是泰氏侧褶蛙（P. thaul）的3.4倍。然而，这两个物种经传统染色后的核型几乎相同。在短头侧褶蛙的中期染色体中，染色质的包装程度明显高于泰氏侧褶蛙。C带分析显示，短头侧褶蛙核型中的组成型异染色质几乎是泰氏侧褶蛙核型中的6倍。荧光带型分析表明，短头侧褶蛙的染色体含有富含AT和GC的异染色质，而泰氏侧褶蛙的核型中没有明亮荧光的异染色质。侧褶蛙属基因组大小的显著差异是由所有染色体上所有DNA序列类别的数量均匀、对称变化所解释的，这些变化保留了染色体的祖先形态。
