Lykkesfeldt A E, Andersen H A
J Cell Biol. 1974 Aug;62(2):316-21. doi: 10.1083/jcb.62.2.316.
Populations of Tetrahymena pyriformis were grown in a chemically defined medium containing the thymidine analogue 5-bromodeoxyuridine (BUdR). About 65% of the thymidine sites in DNA were substituted by BUdR. During the first generation in the presence of BUdR, all DNA became hybrid. After the following cell division, in about 80% of the cells the second DNA replication round was initiated but no further cell division took place. The cells could be rescued by removing BUdR and adding thymidine. New replication took place before the first cell division. However, although the cells contained double heavy as well as hybrid DNA, only the hybrid DNA was replicated. After a full replication of the hybrid DNA, normal growth was restored. Melting profiles of normal, hybrid, and double heavy DNA indicated a structural change of the double heavy DNA.
梨形四膜虫群体在含有胸腺嘧啶类似物5-溴脱氧尿苷（BUdR）的化学限定培养基中生长。DNA中约65%的胸腺嘧啶位点被BUdR取代。在存在BUdR的第一代中，所有DNA都变成了杂种DNA。在接下来的细胞分裂后，约80%的细胞开始了第二轮DNA复制，但没有进一步的细胞分裂发生。通过去除BUdR并添加胸腺嘧啶可以挽救这些细胞。新的复制在第一次细胞分裂之前发生。然而，尽管细胞中含有双重重DNA以及杂种DNA，但只有杂种DNA被复制。杂种DNA完全复制后，恢复了正常生长。正常DNA、杂种DNA和双重重DNA的解链图谱表明双重重DNA发生了结构变化。
