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

摘要

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.