7
ment, results in a decrease in mitochondrial density and function (33).
Mutants that completely lack plastids (aplastidic) have been produced by
treatment with streptomycin, heat, or ultraviolet light (34,35). These
permanently bleached cells are perfectly viable as long as they are
grown on a carbon source which can be respired. This makes it feasible
to distinguish processes controlling mitochondrial development from those
controlling chloroplast development.
This dissertation concerns itself with studies of mitochondrial RNA
synthesis in Euglena gracilis and is directed towards elucidating the
components of the transcriptional process, in particular, characterizing
the mitochondrial DNA dependent RNA polymerase with a view toward under
standing the control of transcription. The RNA synthesizing activity of
isolated mitochondria has been studied and the DNA dependent RNA polymerase
has been solubilized and partially purified. The experimental approach
in this study was to develop a method for preparing highly purified mito
chondria, to study the incorporation of labeled ribonucleoside triphosphate
precursors into RNA by isolated mitochondria and to identify the labeled
products. The mitochondrial DNA-directed RNA polymerase was partially
purified by ion exchange chromatography. The enzyme activity was charac
terized to determine its requirements for product synthesis and to compare
it to nuclear activities with respect to these requirements.