Schmid M, Feichtinger W, Steinlein C, Nanda I, Mais C, Haaf T, Visbal García R, Fernández Badillo A
Department of Human Genetics, Biocenter, University of Würzburg, Würzburg, Germany.
Cytogenet Genome Res. 2002;96(1-4):228-38. doi: 10.1159/000063016.
The chromosomes of the rare South American marsupial frogs Gastrotheca walkeri and G. ovifera were extensively reexamined with various banding techniques. The karyotypes of both species are distinguished by a new category of XY female symbol /XX male symbol female sex chromosomes. The unusual Y chromosomes are characterized by containing the least amount of constitutive heterochromatin in the karyotypes. This is in contrast to all previously known amphibian Y chromosomes and does not fit the evolutionary model of early XY differentiation in vertebrates. In male meiosis, the heteromorphic XY chromosomes of both species still exhibit the same pairing configurations as the autosomes. DNA flow cytometric measurements show the nuclear DNA amount of G. walkeri to be 10.90 pg. The significance of the XY/XX sex chromosomes of these marsupial frogs, the various classes of constitutive heterochromatin detected, and the data obtained from meiotic analyses are discussed in detail.
利用各种显带技术对珍稀的南美有袋蛙沃氏胃蛙（Gastrotheca walkeri）和卵形胃蛙（G. ovifera）的染色体进行了广泛的重新研究。这两个物种的核型都以一种新的XY雌性/XX雄性性染色体类别为特征。异常的Y染色体的特点是在核型中所含的组成型异染色质最少。这与所有先前已知的两栖动物Y染色体形成对比，不符合脊椎动物早期XY分化的进化模型。在雄性减数分裂中，这两个物种的异型XY染色体仍表现出与常染色体相同的配对构型。DNA流式细胞仪测量显示沃氏胃蛙的核DNA含量为10.90皮克。详细讨论了这些有袋蛙的XY/XX性染色体的意义、检测到的各种组成型异染色质类别以及从减数分裂分析中获得的数据。
