Degree Type


Date of Award


Degree Name

Doctor of Philosophy



First Advisor

Richard L. Hallberg


Tetrahymena thermophila is a fresh water, ciliated protozoan that is able to regulate the expression of various sets of genes in response to physiological changes. When cells are transferred from their normal growth medium to starvation medium, cell division is arrested. When cells are transferred back to growth medium, cells are able to resume dividing. If cells are heat shocked at 41°C or above, cells are not able to divide at these temperatures, but if returned to 30°C, will resume dividing. The environmental condition in which the cells are placed can dramatically effect cell division;In this study, we have characterized the accumulation of a 1460 nucleotide long, poly A+ RNA that is induced to become an abundant RNA in non-dividing cells. This RNA, called C5, is not present in growing cells, but accumulates during starvation, heat shock, and during stationary growth. These conditions will cause cell division to be arrested. When cells are allowed to resume dividing, the concentration of C5 RNA drops rapidly as cells begin dividing. For this RNA to be accumulated and maintained, ongoing protein synthesis is required, but not continued DNA replication. Although this RNA has some properties of a poly A+ mRNA, our evidence suggests that C5 RNA does not encode a peptide. The function of this RNA in division arrested cells is not known.



Digital Repository @ Iowa State University,

Copyright Owner

Stephen James Libby



Proquest ID


File Format


File Size

95 pages

Included in

Zoology Commons