MUTANTS WITH ALTERED Ca²⁺-CHANNEL PROPERTIES IN PARAMECIUM TETRAURELIA: ISOLATION, CHARACTERIZATION AND GENETIC ANALYSIS

Robert D. Hinrichsen ¹, Yoshiro Saimi ¹, and Ching Kung ²

¹ Laboratory of Molecular Biology, University of Wisconsin-Madison, Madison, Wisconsin 53706
² Laboratory of Molecular Biology, Department of Genetics, University of Wisconsin-Madison, Madison, Wisconsin 53706

Dancers are a group of mutants in Paramecium tetraurelia whose Ca²⁺ current inactivates poorly and are likely to be defective in the structure of their Ca²⁺ channels. These mutants show prolonged backward swimming in response to K⁺ and Ba ²⁺ in the medium and were selected by this property in a galvanotactic trough. The dancer mutants are semidominant, and all isolated mutants belong to one complementation group; they are not allelic to any of the previously isolated behavioral mutants of P. tetraurelia. The phenotypic change from the homozygous parent to heterozygous F₁ generation takes three to five fissions. There is no evidence of a cytoplasmic factor capable of converting the dancer to the wild-type phenotype, as has been demonstrated in the mutants pawn and cnr. We suggest that the dancer locus is a structural gene for the Ca²⁺ channel.

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