CONSERVATION AND CHROMOSOMAL LOCALIZATION OF DNA SATELLITES IN BALENOPTERID WHALES
CONSERVATION AND CHROMOSOMAL LOCALIZATION OF DNA SATELLITES IN BALENOPTERID WHALES
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DOI：
10.1007/bf00295136
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发表时间：
1978-01-01
期刊：
影响因子：
1.6
通讯作者：
JONES, KW
中科院分区：
文献类型：
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作者：
ARNASON, U;PURDOM, IF;JONES, KW
从尖喙Balaenopters acutorostrata、B. borealis，B.酸浆。至少2个DNA卫星在每个中可识别，在中性CsCl中具有ρ的浮力密度。= 1.702/1.703和ρ. = 1.710/1.711。来自每个卫星组的互补[c]RNA用于过滤和原位杂交。同源和异源的DNA-cRNA杂交在每个卫星组产生几乎相同的熔解曲线的轮廓显示至少相当一部分的DNA卫星序列的保护。在rho. = 1.702/1.703且ρ= 1.710/1.711卫星。在每个物种中，Rho。= 1.702/1.703卫星位于少数对的着丝粒-副着丝粒C[组成型异染色质]带中，而ρ. = 1.710/1.711的随体位于染色体的末端C带。卫星DNA序列的数量进化明显早于种间分化，分化发生后卫星序列保持相对不变。卫星DNA的功能被认为意味着引入染色体和基因多态性，因此在物种形成中具有重要意义。基于这些概念，卫星DNA的功能的模型被假定。根据这个模型，在减数分裂配对时，同源染色体之间的常染色质-异染色质重叠被认为是普遍发生的。这种重叠被认为是加重的同源异染色质片段（C带）之间经常观察到的大小异形。在这种常染色质-异染色质重叠的区域中，将排除交换。重叠被认为是在染色体臂中逐步纠正，离开不受影响的交换远常染色质异染色质交界处。因此，在连接点附近的基因被集体遗传和选择，而远离异染色质的基因被独立分类和选择。
DNA satellites were isolated from 3 balenopterid species, Balaenopters acutorostrata, B. borealis, B. physalus. At least 2 DNA satellites were recognizable in each with buoyant densities in neutral CsCl of .rho. = 1.702/1.703 and .rho. = 1.710/1.711, respectively. Complementary[c]RNA from each satellite group were used for filter and in situ hybridizations. Homo- and heterologous DNA-cRNA hybrids within each satellite groups yielded virtually identical melting curve profiles showing conservation of at least a considerable part of the DNA satellite sequences. There was no evident sequence homology between the .rho. = 1.702/1.703 and the .rho. = 1.710/1.711 satellites by filter hybridization. In each species the .rho. = 1.702/1.703 satellite was located in centromeric-paracentromeric C[constitutive heterochromatin]-bands in a few pairs, whereas the .rho. = 1.710/1.711 satellite was located in terminal C-bands throughout the karyotypes. The quantitative evolution of the satellite DNA sequences apparently preceded species divergence of the balenopterids and the satellite sequences have remained relatively unaltered since the divergence took place. The function of satellite DNA is considered to imply the introduction of both chromosomal and genic polymorphisms and thus being of great importance in speciation. Based upon these concepts a model is postulated for the function of satellite DNA. According to this model at meiotic pairing euchromatin-heterochromatin overlapping between homologous chromosomes is considered to be of a general occurrence. This overlapping is presumed to be accentuated by the size heteromorphism frequently observed between homologous heterochromatic segments (C-bands). In the region of such euchromatin-heterochromatin overlapping, crossing-over would be excluded. The overlapping is suggested to be rectified progressively in the chromosome arms, leaving unaffected crossing-over distant to the euchromatin-heterochromatin junctions. Genes in the proximity of the junctions are therefore collectively inherited and selected, whereas genes distant to the heterochromatin are independently assorted and selected.