Bozzoni I, Beccari E
Biochim Biophys Acta. 1978 Sep 27;520(2):245-52. doi: 10.1016/0005-2787(78)90224-1.
We have compared the amount of clustered and interspersed repetitive sequences in the genome of four Amphibia with different DNA contents per haploid nucleus: two Anura (Xenopus laevis, 3 pg and Bufo bufo, 7 pg) and two Urodela (Triturus cristatus, 23 pg and Necturus maculosus, 52 pg). High molecular weight DNA of the four species was denatured and reassociated to the same Cot in order to obtain duplex sequences with a similar reiteration frequency. Single-stranded DNA was digested off with the Aspergillus S1 nuclease. DNA was then fractionated according to the molecular weight through an agarose A-50 column. We found that the amount of long repetitive sequences is roughly proportional to the genome size in the four species, while the number of short (about 300 base pairs) repetitive sequences is increased many-fold in the species with the larger DNA content, both in Anura and in Urodela.
我们比较了四种两栖动物基因组中聚类和散布的重复序列的数量，这四种两栖动物每个单倍体细胞核的DNA含量不同：两种无尾目动物（非洲爪蟾，3皮克；中华大蟾蜍，7皮克）和两种有尾目动物（ cristatus蝾螈，23皮克；斑点钝口螈，52皮克）。将这四个物种的高分子量DNA变性并复性至相同的Cot值，以获得具有相似重复频率的双链序列。用曲霉S1核酸酶消化单链DNA。然后通过琼脂糖A-50柱根据分子量对DNA进行分级分离。我们发现，在这四个物种中，长重复序列的数量大致与基因组大小成正比，而短（约300个碱基对）重复序列的数量在DNA含量较大的物种中增加了许多倍，在无尾目和有尾目中都是如此。
