title: Chromosome-designated mutation selection in Tetrahymena thermophila.
abstract: Two protocols are presented that allow the selection of mutations mapping to micronuclear chromosome 5 in Tetrahymena thermophilia. One protocol involves crossing mutagenized diploid cells directly to a strain nullisomic for chromosome 5 and screening the monosomic progeny for a mutant phenotype. The second protocol first takes the mutagenized diploid cells through round I of genomic exclusion to create useful and reusable mutant heterokaryons, which are then assayed for the presence of mutations on chromosome 5 by crossing to the nullisomic 5 strain. Of 14 putative chromosome 5 mutations obtained by these two methods, seven are shown by genetic analysis to be recessive mutations on chromosome 5; one mapped elsewhere in the genome; six were infertile or failed to yield progeny in some of the diagnostic crosses and, thus, their genetic nature could not be determined with certainty.
mesh_terms: D000818:Animals; D002875:Chromosomes / Q000502:physiology*; D003433:Crosses, Genetic; D004171:Diploidy; D009154:Mutation; D010641:Phenotype; D012641:Selection, Genetic; D013045:Species Specificity; D013768:Tetrahymena / Q000235:genetics*