Linkage of Mutations Affecting minus Flagellar Membrane Agglutinability to the mt Mating-Type Locus of Chlamydomonas.

Two independently isolated mutant strains, imp-10 and imp-12, were obtained by UV irradiation of wild-type mating-type minus (wt(-)). Each fails to agglutinate sexually with gametes of either mating type, but mating and zygote formation can be elicited by agglutinating either strain to wt(+) gametes by means of anti-flagellar antiserum. Tetrad analysis of the resultant zygotes shows that both imp-10 and imp-12 are very closely linked to mt(-), with no recombinants observed. Diploid strains constructed between imp-10 or imp-12 and wt(+) gametes are wt(-), that is, they agglutinate and fuse like normal minus cells. Tetrad analysis of triploids from imp-10 diploid x wt(+) haploid crosses shows that only imp-10 and wt(+) products are recovered. A model is proposed to account for these results.