Linkage analysis in Dictyostelium discoideum using multiply marked tester strains: establishment of linkage group VII and the reassessment of earlier linkage data.

To aid linkage analysis and mapping studies in Dictyostelium discoideum, we have constructed several tester strains with easily scored mutations characterizing the six currently identified linkage groups. Use has been made of conditionally lethal mutants unable to grow upon Bacillus subtilis, and the locus of the mutation involved (bsgA) has been assigned to linkage group III. The mutation cobA1, which confers resistance to cobaltous chloride, has been assigned to a previously unidentified linkage group (VII). The temperature-sensitive growth mutation tsgC7, previously reported to define linkage group V, has been reassigned to group III, leaving linkage group V presently unmarked. The further use of genetic tester strains is described.