CHROMOSOME BREAKAGE ACCOMPANYING GENETIC RECOMBINATION IN BACTERIOPHAGE

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Abstract
Experiments designed to detect original parental DNA in recombinant phages were carried out. Density-gradient centrifugation was used to determine the distribution of labeled parental DNA among both parent and recombinant genotypes emerging from a 2-factor cross between unlabeled phage [lambda] and [lambda]heavily labeled with the isotopes C13 and N15. The results demonstrate the presence of preferred quantities of original parental DNA in recombinant phages and support the following main conclusions (1) The DNA complement of a is contained in a single semiconservatively replicating chromosome. (2) Recombination occurs by chromosome breakage, although other mechanisms are not excluded. (3) Both chromosomal subunits are broken during recombination. (4) Distances along the genetic map are proportional to the amounts of DNA in the phage chromosome. (5) The phage chromosome need not replicate in order to undergo recombination by breakage.[long dash]Auth. summ.