MAPPING 3 CLASSICAL ISOZYME LOCI IN TETRAHYMENA - MEIOTIC LINKAGE OF ESTA TO THE CHXA LINKAGE GROUP

We demonstrate a reliable method for mapping conventional loci and obt aining meiotic linkage data for the ciliated protozoan Tetrahymena the rmophila. By coupling nullisomic deletion mapping with meiotic linkage mapping, loci known to be located on a particular chromosome or chrom osome arm can be tested for recombination. This approach has been used to map three isozyme loci, EstA (Esterase A), EstB (Esterase B), and AcpA (Acid Phosphatase A), with respect to the ChxA locus (cycloheximi de resistance) and 11 RAPDs (randomly amplified polymorphic DNAs). To assign isozyme loci to chromosomes, clones of inbred strains C3 or C2 were crossed to inbred strain B nullisomics. EstA, EstB and AcpA were mapped to chromosomes 1R, 3L and 3R, respectively. To test EstA and Ac pA for linkage to known RAPD loci on their respective chromosomes, a p anel of Round II (genomic exclusion) segregants from a B/C3 heterozygo te was used. Using the MAPMAKER program, EstA was assigned to the ChxA linkage group on chromosome 1R, and a detailed map was constructed th at includes 10 RAPDs, AcpA (on 3R), while unlinked to all the RAPDs as signed to chromosome 3 by nullisomic mapping, does show linkage to a R APD not yet assignable to chromosomes by nullisomic mapping.