Perturbance analysis of nuclear determination in Tetrahymena: analysis of mating type frequency variations with reference to binary-switch models.

To test a 3-switch binary element model of mating type determination all possible assignments of the seven mating types of Tetrahymena thermophila to compound switch states have been examined, using a set of 77 experimentally obtained frequency patterns as a base. None of the assignments gives a satisfactory agreement with all the data. The result is similar whether the eighth switch state is considered forbidden or redundant. Moreover, further explorations of models in which the switches are not independent (as originally proposed), but coupled also fail to reveal a satisfactory agreement. Finally some 4-switch models are examined, again without discovering a satisfactory fit, though some evidence of structural relationship among the mating types is provided. The system is more complex than was assumed by the original models. To carry out this analysis certain statistical problems of a more general interest required solution. These include the management of samples from multinomial populations and the provision of efficient estimators for models of this sort.