No abstract

Thirty previously unmapped markers have been located; 13 are at newly designated loci. Numerous sequences for previously mapped genes have also been determined. A revised map of linkage group I is presented. The order from conventional mapping has been confirmed by testing recessive markers in IL for coverage by duplications. Assignment of new mutants to linkage groups is greatly facilitated by using gene-tagged multiple translocation strains for linkage detection; these "alcoy" tester strains and procedures for using them are described. Recent mapping data of other workers are compiled. Distal markers are now known for all but one of the 14 chromosome arms, but extensive map segments are still devoid of markers.

Neurospora crassa strains of opposite mating type are ordinarily heterokaryon-incompatible during vegetative growth. An unlinked mutant called tolerant (tol) is described, which suppresses the vegetative incompatibility of unlike mating types without affecting their ability to cross. The mutant tol was selected and studied by means of duplications heterozygous for mating type. Use of the duplication eliminates complications due to unlinked heterokaryon genes. The mode of action of tol has been confirmed by conventional heterokaryon tests. tol has been mapped in linkage group IV, close to tryp-4. A suppressor similar or identical to tolerant has been found in a wild strain from Panama, out of 14 different wild types which were tested. By using a different duplication which covers the unlinked heterokaryon-compatibility locus C, it was shown that tolerant does not suppress C/c incompatibility. The fact that tolerant suppresses only one of the two functions ascribed to mating type revives the question of whether 'mating-type' is one gene or two. However, the data strongly support Pittenger's (1957) conclusion that, if two genes are involved, they must be closely linked.

No abstract

No abstract