Molecular mechanisms of genetic recombination in bacteriophage: VI. A mutant defective in the joining of DNA molecules

Abstract

DNA was extracted from Escherichia coli BB infected with a mixture of 32P-labelled and bromouracil-labelled T4 amA453 (a mutant of gene 32 defective in DNA synthesis) after incubation for 60 to 120 minutes. Analysis by caesium chloride density-gradient centrifugation of the DNA showed no 32P label in the heavier molecules as produced in a similar cross with amN82 (gene 44) or am × 5 (genes 41 to 45) by the joining of parental DNA molecules. The activities of several early enzymes induced by phage infection were measured with the extracts of cells infected with amA453. The infection induced the syntheses of phage-specific DNA-polymerase and deoxycytidine triphosphate pyrophosphatase. Deoxyribo-nuclease activity increased after the infection. These results show that the function of gene 32 is necessary for the formation of joint molecules, and the function is in some way related to the replication of phage DNA.