METHODS FOR ANALYSIS OF THE C-CISTRON OF TEMPERATE PHAGE-16-3 OF RHIZOBIUM-MELILOTI

Orosz, László (1980) METHODS FOR ANALYSIS OF THE C-CISTRON OF TEMPERATE PHAGE-16-3 OF RHIZOBIUM-MELILOTI. Genetics, 94 (2). pp. 265-276. ISSN 0016-6731 (print), 1943-2631 (online)

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Abstract

A series of clear mutants of the temperate phage 16-3 of Rhizobium meliloti were isolated that included various point and deletion mutants ofthe Ccistron, coding for the phage repressor. It was observed that recombinant genotypes, such as c+ and ti (temperature-sensitive allele), which form turbid plaques, can be detected quantitatively as lysogenic colonies and scored even at frequencies as low as 10-6. Point mutations, deletions and the autonomy of intracistronic second-site mutations were characterized by this method. Further analysis has shown that each possible pair from three ti mutants gave non-conditional clear recombinants. It was shown that these latter bear the two initial ti mutations, suggesting a cumulative effect of two conditional mutations on the structure of the repressor protein. The double mutants were utilized in fine-structure mapping of the Ccistron.

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