The regulation of amounts and proportions of genetic elements in the macronuclei of Tetrahymena thermophila strains of diverse karyotype.

Measurements of the micronuclear DNA content of clones with assumed different degrees of micronuclear ploidy confirmed the triploid nature of one clone. The micronuclear DNA content of a presumptive haploid clone was found to be slightly higher than expected, whereas one of two aneuploid clones had an unexpectedly low micronuclear DNA content. The macronuclear DNA content of cells with macronuclei which had developed from triploid, diploid and probably haploid and aneuploid macronuclear-Anlagen is very similar. Specifically, the smallest individual macronuclear DNA contents are consistently found within the same size class in all clones tested. Cell volumes, RNA and protein contents are alike in all clones tested. Only the growth rate and maximal density reached of one out of two aneuploid clones is reduced in comparison with the very similar other clones. The results are discussed with reference to the regulation of macronuclear DNA content, and to the compensation of gene-dosage.