Schmid M, Ziegler C G, Steinlein C, Nanda I, Haaf T
Department of Human Genetics, Biocenter, University of Würzburg, Würzburg, Germany.
Cytogenet Genome Res. 2002;97(3-4):205-18. doi: 10.1159/000066615.
The mitotic chromosomes of an Ecuadorian population of the marsupial frog Gastrotheca espeletia were analyzed by means of banding techniques and fluorescence in situ hybridization. This species is characterized by unusual supernumerary (B) chromosomes. The maximum number of B chromosomes is 9 and they occur in three different morphological types. Banding analyses show that the B chromosomes are completely heterochromatic, consist of AT base pair-rich repeated DNA sequences, replicate their DNA in very late S-phase of the cell cycle, and are probably derived from a centromeric or paracentromeric region of a standard (A) chromosome. Exceptionally, the B chromosomes carry 18S + 28S ribosomal RNA genes and the conserved vertebrate telomeric DNA sequence appears to be underrepresented. Flow cytometric measurements of the nuclear DNA content differentiate between individuals with different numbers of B chromosomes. Significantly more B chromosomes are present in female than in male animals.
通过显带技术和荧光原位杂交分析了厄瓜多尔有袋蛙 Gastrotheca espeletia 种群的有丝分裂染色体。该物种的特征是具有不寻常的超数（B）染色体。B 染色体的最大数量为 9 条，且存在三种不同的形态类型。显带分析表明，B 染色体完全是异染色质的，由富含 AT 碱基对的重复 DNA 序列组成，在细胞周期的 S 期晚期复制其 DNA，并且可能源自标准（A）染色体的着丝粒或近着丝粒区域。特别的是，B 染色体携带 18S + 28S 核糖体 RNA 基因，而保守的脊椎动物端粒 DNA 序列似乎含量不足。对核 DNA 含量的流式细胞术测量区分了具有不同数量 B 染色体的个体。雌性动物中的 B 染色体数量明显多于雄性动物。
