A comparison of two-point, three-point and deletion mapping in the C cistron of rhizobiophage 16-3, with an explanation for the recombination pattern.
A general tendency for additivity prevailed in recombination frequencies for two-point fine-structure mapping of 14 mutants in the C cistron of Rhizobium meliloti phage 16-3, with little evidence of any marker effect. Intracistronic three-point mapping indicated that double crossovers are rare. Deletion mapping indicated that the two- and three-point mapping data gave the correct order of the mutations. A high frequency (5 to 8%) of c/c(+) heterozygotic phage progenies was observed in standard crosses. This pattern implies formation of a relatively long region of heterozygosity. Together with the results of the three-point tests, it suggests certain properties of the branch migration and resolution steps envisioned in current mechanisms of recombination.
Orosz
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Attila József University, Department of Genetics, H-6726 Szeged, Középfasor 52, Hungary.
Rostás
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Hotchkiss
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