Johnston L H, Thomas A P
Mol Gen Genet. 1982;186(3):439-44. doi: 10.1007/BF00729466.
Sixty-eight new conditional cell cycle mutants have been isolated on the basis of their terminal cellular morphology ('dumbbells'). Fifteen mutants falling into nine complementation groups, were grossly defective in DNA replication and have been assigned the provisional gene symbol dbf (for dumbbell former). Dbf1 and 2 stop DNA synthesis immediately on transfer to 37 degrees C and are presumably defective in enzymes required for polymerization. Neither, however, possess a thermolabile DNA polymerase A or B. Dbf3 and 4 show a pattern of synthesis consistent with their being deficient in initiation of DNA synthesis. This is confirmed in the accompanying paper. The remaining mutants are deficient in the synthesis of RNA as well as DNA. Indeed the four members of one complementation group are allelic with rna3, one of the group of mutants originally isolated as defective in RNA synthesis, and which do not exhibit a cell cycle phenotype. A re-examination of this group of mutants, however, showed the bulk of them also to be defective in DNA synthesis. Furthermore, in preliminary experiments rna3 and our four new alleles of it, together with rna6 and dbf5 and 6, showed enhanced spontaneous mutation frequency.
基于其终末细胞形态（“哑铃状”），已分离出68个新的条件性细胞周期突变体。15个突变体分为9个互补群，在DNA复制方面存在严重缺陷，并被赋予临时基因符号dbf（意为“哑铃形成者”）。Dbf1和2在转移至37℃时立即停止DNA合成，推测在聚合所需的酶方面存在缺陷。然而，它们都不具有热不稳定的DNA聚合酶A或B。Dbf3和4显示出一种合成模式，表明它们在DNA合成起始方面存在缺陷。这在随附论文中得到证实。其余突变体在RNA和DNA合成方面均存在缺陷。实际上，一个互补群的四个成员与rna3等位，rna3是最初作为RNA合成缺陷而分离出的一组突变体之一，且不表现出细胞周期表型。然而，对这组突变体的重新检查表明，它们中的大多数在DNA合成方面也存在缺陷。此外，在初步实验中，rna3及其四个新等位基因，连同rna6以及dbf5和6，显示出自发突变频率增加。
