Macronuclear Subunits of Tetrahymena thermophila Are Functionally Haploid
F. PAUL DOERDER 1,
JONATHAN H. LIEF 1, and
L. E. DEBAULT 2
1 Department of Life Sciences, University of Pittsburgh, Pittsburgh, Pennsylvania 15260
2 Department of Pathology, University of Iowa, Iowa City 52242
In Tetrahymena thermophila the major argument for the existence of diploid subunits has been that some loci show a delay in the accumulation of stable subclones during macronuclear assortment. This delay is based on the assumption that throughout the life cycle there are 45 subunits. We find that for at least 50 fissions after conjugation there is sufficient DNA for 66 haploid subunits. These additional subunits early in the life cycle are sufficient to explain the observed accumulation of stable subclones in all instances. This removes the need to invoke diploidy to explain assortment, thus resolving the question of subunit ploidy in favor of haploidy.
Submitted on March 22, 1977
Revised on July 18, 1977
