Molecular cytogenetic studies on the process of genomic and chromosomal reorganization in amphibians and reptiles

为了描述四足动物的基因组和核型进化过程，我们构建了中华盘螺、暹罗鳄、四条锦蛇、拯救巨蜥、热带爪蟾和非洲爪蟾的比较细胞遗传学图谱。我们的研究结果提供了一种可能性，即四足动物的祖先核型至少有10个大型连锁群的大染色体和许多微染色体对，这已在鸡中保守。我们鉴定了光肩星天牛的所有9个同源染色体组，除两个倒位外，它们在同一组内都是同源的，并且在光肩星天牛之间的遗传连锁是高度保守的。tropicalis和X.除了一个融合和一个倒置。在大肠在quadrivirgata中，微染色体基因显示出比鸡中的大染色体基因显著更高的GC含量，这表明染色体大小依赖的GC异质性已经在2.75亿年前的鳞龙-祖龙分裂之前发生。

To delineate the process of genomic and karyotypic evolution of tetrapods, we constructed comparative cytogenetic maps of Pelodiscus sinensis, Crocodylus siamensis, Elaphe quadrivirgata, Varanus salvator, Xenopus tropicalis, and Xenopus laevis. Our results provide the possibility that the ancestral karyotype of tetrapods had at least 10 large linkage groups of macrochromosomes and many microchromosomal pairs, which have been conserved in the chicken. We identified all nine homoeologous chromosome groups of X laevis, which were homologous within the same groups except for two inversions, and the genetic linkages were highly conserved between X. tropicalis and X. laevis except for one fusion and one inversion. In E. quadrivirgata, microchromosomal genes showed significantly higher GC content than macrochromosomal genes as in the chicken, suggesting that the chromosome size-dependent GC heterogeneity had already occurred before the lepidosaur-archosaur split, 275 million years ago.