Bertani G, Chattoraj D K
Nucleic Acids Res. 1980 Mar 25;8(6):1339-56. doi: 10.1093/nar/8.6.1339.
From a tandem duplication mutant of phage P2, triplication, quadruplication and pentuplication forms were derived. They were recognized by decreased virion heat stability resulting from the increase in DNA content, and were confirmed by electron microscope heteroduplex mapping. These forms of partially repeated DNA are quite stable in P2 because of the low level of recombination typical of this phage. Under conditions normally employed for full DNA renaturation, these high order repeat chromosomes gave often incomplete renaturation over the repeated segments. Based on current models for DNA renaturation, several predictions were made and tested. The results, although not quantitatively exhaustive, indicated that base pairing proceeding from a nucleation site was sufficiently slow to allow a second nucleation to occur with a fair probability over a length of a few thousand base pairs.
从噬菌体P2的串联重复突变体中，衍生出了三倍体、四倍体和五倍体形式。它们通过病毒粒子热稳定性降低（这是由于DNA含量增加所致）得以识别，并通过电子显微镜异源双链图谱分析得到证实。由于这种噬菌体典型的低重组水平，这些部分重复DNA形式在P2中相当稳定。在通常用于DNA完全复性的条件下，这些高阶重复染色体在重复片段上常常出现不完全复性。基于当前的DNA复性模型，做出了几个预测并进行了测试。结果虽然在数量上并不详尽，但表明从成核位点开始的碱基配对足够缓慢，以至于在几千个碱基对的长度上，相当有可能发生第二次成核。
