Kubota S, Nakai Y, Kuro-o M, Kohno S
Department of Biology, Faculty of Science, Toho University, Japan.
Cytogenet Cell Genet. 1992;60(3-4):224-8. doi: 10.1159/000133345.
Cytogenetic studies were performed on two types of Japanese hagfish (Eptatretus okinoseanus) that eliminate about 45% (type A) and 55% (type B) of their DNA from presumptive somatic cells during the differentiation of somatic cells. The observations revealed inter- and intraindividual variations in the number of chromosomes in germ cells of both types of hagfishes. Although the modal number of chromosomes in the germ cells was 54 in both types, the percentage of cells with the modal number was rather low (38.6% [51/132] in five specimens of type A and 22.7% [25/110] in eight specimens of type B). In addition, one of seven type B specimens clearly had a modal number of 62 chromosomes. Another specimen of type B had a bimodal distribution of chromosome numbers, with peaks of 54 and 59 chromosomes. The observation of interindividual variations was supported by data on the amount of DNA in germ cells of type B specimens. However, these variations were rarely observed in somatic cells. These results suggest that supernumerary (B) chromosomes are maintained in germ cells and are eliminated together with some other chromosomes and/or chromatin from somatic cells.
对两种日本盲鳗（Eptatretus okinoseanus）进行了细胞遗传学研究，这两种盲鳗在体细胞分化过程中会从假定的体细胞中消除约45%（A型）和55%（B型）的DNA。观察结果显示，两种盲鳗生殖细胞中的染色体数量存在个体间和个体内差异。尽管两种类型的生殖细胞中染色体的众数均为54，但具有众数染色体数的细胞百分比相当低（A型的五个样本中为38.6%[51/132]，B型的八个样本中为22.7%[25/110]）。此外，七个B型样本中的一个明显具有62条染色体的众数。另一个B型样本的染色体数呈双峰分布，峰值分别为54条和59条染色体。B型样本生殖细胞中DNA含量的数据支持了个体间差异的观察结果。然而，这些差异在体细胞中很少观察到。这些结果表明，超数（B）染色体在生殖细胞中得以保留，并与其他一些染色体和/或染色质一起从体细胞中消除。
