The Japanese Journal of Genetics

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The structure of chromosomes of phage and bacteria and their recombination are discussed from the standpoint of molecular genetics.
Each T-even phage particle has a single molecule of DNA on which all the known genetic markers are linked to form a continuous linear genetic-map. Upon injection, genes on a chromosome may be injected into a bacterium at a fixed order. Experiments with chloramphenicol showed that multiplying phage chromosomes are composed of DNA to the exclusion of all the known phage constituents.
As to genetic recombination, there are two lines of approach: one is physical, chemical and genetic analysis of recombinant chromosomes, and the other is to analyze the mechanism physiologically. Researches along the first line showed that the genetic recombination may occur by breakage of phage chromosomes. While the other line of researches revealed rather simple nature of the mechanism.
Similarities of genetic phenomena between phage and bacteria are also pointed out.
Besides the results already published, the following results of our recent experiments are presented. (1) After the decay of P³² incorporated into DNA, phage T2 injects its chromosome partly: genetic analysis of the markers thus injected suggests a fixed order of injection of genes. (2) Crosses were made between phage T2h labeled with P³² and nonlabeled T2h⁺. P³² transferred in specific association with the h marker is measured. Statistical analysis of the results suggest that less than 15% of transferred P³² is associated specifically with the h marker. (3) Bacteria were infected with phage T2 labeled with P³² and then DNA samples were prepared from the infected bacteria at various times after infection. Labeled phage DNA isolated from the infected bacteria completely resists to polydeoxynuclease, as well as the DNA directly prepared from phage particles, even after sonication. (4) Genetic recombination of phage T4 takes place in the presence of chloramphenicol or 5-fluorodeoxyuridine. Its occurence is suggested even under the treatment with KCN. (5) Genetic recombination of bacteria takes place in the presence of 5-fluorodeoxyuridine.

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