Rec-Mediated Recombinational Hot Spot Activity in Bacteriophage Lambda Ii. A Mutation Which Causes Hot Spot Activity

Crosses have been performed which identify phage mutants (chi) which cause recombinational hot spot activity in lambda. The hot spot activity is found in crosses of red(-) gam(-) chi(-) strains in rec(+) hosts; in the crosses reported here, both the chi(-) mutations and the hot spot are located near the right end of the chromosome. The hot spot occurs in standard crosses as well as under conditions which block DNA synthesis, and is dependent on a functional host recB gene.-The chi mutation is shown to be dominant, but the tests do not show whether chi is a gene or a site.