INTEGRATED MAPS OF THE CHROMOSOMES IN DICTYOSTELIUM-DISCOIDEUM

Detailed maps of the six chromosomes that carry the genes of Dictyoste lium discoideum were constructed by correlating physically mapped regi ons with parasexually determined linkage groups. Chromosomally assigne d regions were ordered and positioned by the pattern of altered fragme nt sizes seen in a set of restriction enzyme mediated integration-rest riction fragment length polymorphism (REMI-RFLP) strains each harborin g an inserted plasmid that carries sites recognized by NotI, SstII, Sm aI, BglI and ApaI. These restriction enzymes were used to digest high molecular weight DNA prepared from more than 100 REMI-RFLP strains and the resulting fragments were separated and sized by pulsed-held gels. More than 150 gene probes were hybridized to blots of these gels and used to map the insertion sites relative to flanking restriction sites . In this way, we have been able to restriction map the 35 mb genome a s well as determine the map position of more than 150 genes to with si milar to 40 kb resolution. These maps provide a framework for subseque nt refinement.