Viscoelastic studies on Tetrahymena macronuclear DNA.

We have used viscoelastometry in an attempt to understand the physical organization of genetic material in Tetrahymena nuclei. The micronucleus or germ line nucleus is diploid. It divides mitotically during vegetative growth, and five pairs of chromosomes are seen in meiosis. The macronucleus, or somatic nucleus, is approximately 45-ploid, divides amitotically, and has no visible chromosomes at any stage. Viscoelastic analysis of Tetrahymena macronuclei reveals DNA Molecules of 2-3 X 10(10) daltons accounting for much, if not all, of the macronuclear DNA. Since the average chromosome in the micronucleus contains 2.4-2.7 X 10(10) daltons of DNA, we deduce that the macronucleus of Tetrahymena contains chromosome-sized DNA molecules.