FUNDAMENTAL STUDIES OF DNA DIMINUTION (CHROMOSOME ELIMINATION) IN LOWER FISH DURING DIFFERENTIATION INTO SOMATIC CELLS.

四种日本和一种东太平洋加拿大盲鳗目（Myxinida，Eptatretus okinoseanus，Eptatretus burgeril Paramyxine热海，Myxine garmani和Eptatretus stoutil）的生殖细胞（精母细胞和精原细胞）与体细胞（肝、血、鳃和肾）的染色体数目不同。精原细胞（54、52、48、16和54）与体细胞（34、36、34、14和34）的染色体数目之差分别为20、16、14、2和20; okinoseanus、E. burgeri、热海拟青霉（P. atami）、M. garmani和E. stoutii，分别。在大肠在okinoseanus中，观察到两种类型的生殖细胞，即具有大量C阳性染色质的生殖细胞和具有少量C阳性染色质的生殖细胞。从生殖细胞中去除的DNA相对量平均为43.6%（E. O. A型）、55.1%（E. O. B型）、20.9%（E. B.），40.0%（P.a.），29.8%（M. g.）和48.7%（E. s.），分别这些结果清楚地表明，在生活在日本和加拿大的五种盲鳗中， ...更多信息 在太平洋沃茨中，染色体的消除发生在卵裂的早期阶段，但原始生殖细胞除外。okinoseanus（A型，B型）、E. burgeri和M.用30种限制性内切酶进行酶切。两种酶（BamH I和Dra I）在两种大肠杆菌中均产生了仅限于生殖系DNA的弱条带。琼脂糖凝胶电泳。DNA滤膜杂交实验证明，只有在去除的大肠杆菌DNA中才含有两个约125 bp的DNA片段。okinoseanus的基因组DNA占生殖细胞总DNA的1.25%和1.32%。这些值分别对应于二倍体中约8.5 × 10^5和9.0 × 10^5个拷贝。这些片段几乎不包含在其他两个物种的生殖细胞基因组和体细胞基因组。原位杂交实验表明，该DNA片段位于两种类型的生殖细胞中的几条小染色体上，这些染色体在E.冲绳少

Four Japanese and one East Pacific Canadian hagfish in the order Myxinida, Eptatretus okinoseanus, Eptatretus burgeril Paramyxine atami, Myxine garmani and Eptatretus stoutil have been possess different chromosome numbers in their germ cells (spermatocytes and spermatogonia) from somatic cells (liver, blood, gill and kidney). The difference of the chromosome numbers between spermatogonia (54, 52, 48, 16 and 54) and somatic cells (34, 36, 34, 14 and 34) was 20, 16, 14, 2 and 20, in E. okinoseanus, E. burgeri, P. atami, M. garmani and E. stoutii, respectively. In E. okinoseanus, two types of germ cells, those having large amount of C-positive chromatin and those having small amount were observed. The relative amount of DNA eliminated from germ cells averaged 43.6%, (E. o. type A), 55.1% (E. o. type B), 20.9% (E. b.), 40.0% (P. a.), 29.8% (M. g.) and 48.7% (E. s.), respectively. These results clearly indicate that, in the 5 hagfish species in Myxinida which live in Japanese and Canadian P … More acific waters, chromosome elimination takes place during the early stages of cleavage except for the ancestral germ cells.DNA from germ line cells and somatic cells in E. okinoseanus (type A, type B), E. burgeri and M. garmani bad been isolated and digested with 30 kinds of restriction enzymes. Two enzymes (Bam H I, Dra I) generated weak bands limited to germ line DNA in both types of E. okinoseanus by agarose gel electrophoresis. DNA filter hybridization experiments proved that two DNA fragments by Bam HI, about 125 bp long, are contained only in the eliminated DNA of E. okinoseanus and may account about 1.25% and 1.32% of the total germ line genomic DNA. These values would correspond to approximate 8.5x10^5 and 9.0X10^5 copies in diploid, respectively. These fragments are hardly contained in the germ line genomes and somatic genomes of the other two species. In situ hyubridization experiments demonstrated that this DNA fragments are located on several small chromosomes which are limited in germ cells in both types and which are C-band positive chromatin in E. okinoseanus. Less