title: Genetic background alters dominance relationships between mat alleles in the ciliate Tetrahymena thermophila.
abstract: The pattern of inheritance and mechanism of sex determination can have important evolutionary consequences. We studied probabilistic sex determination in the ciliate Tetrahymena thermophila, which was previously shown to cause evolution of skewed sex ratios. We find that the genetic background alters the sex determination patterns of mat alleles in heterozygotes and that allelic interaction can differentially influence the expression probability of the 7 sexes. We quantify the dominance relationships between several mat alleles and find that A-type alleles, which specify sex I, are indeed recessive to B-type alleles, which are unable to specify that sex. Our results provide additional support for the presence of modifier loci and raise implications for the dynamics of sex ratios in populations of T. thermophila.
authors.affiliation: the Department of Biology and Biochemistry, University of Houston, Houston, TX 77204. Sujal S. Phadke is now at the Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109. Tiago Paixão is now at the Institute of Science and Technology Austria.
authors.forename: Sujal S
authors.initials: SS
authors.lastname: Phadke
authors.forename: Tiago
authors.initials: T
authors.lastname: Paixão
authors.forename: Tuan
authors.initials: T
authors.lastname: Pham
authors.forename: Stephanie
authors.initials: S
authors.lastname: Pham
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: Zufall
mesh_terms: D000483:Alleles; D005075:Biological Evolution; D003433:Crosses, Genetic; D005787:Gene Frequency; D056426:Genetic Loci; D014644:Genetic Variation; D006579:Heterozygote; D012744:Sex Ratio; D016808:Tetrahymena thermophila / Q000235:genetics*
keywords: ciliate; inheritance; mating type; sex determination; sex ratio