Degree Type


Date of Award


Degree Name

Doctor of Philosophy


Genetics, Development and Cell Biology

First Advisor

Jack R. Girton


Mutations at the suppressor of forked, su(f), locus are trans-acting, allele specific suppressors and enhancers of mutations at certain other loci. Su(f) is a trans-acting regulator whose normal product is necessary for proper transcription of these genes. The su(f) product regulates the transcription of transposable elements located within these genes. Our investigation includes a genetic analysis in which a number of new su(f) alleles were isolated, a development analysis in which the effects of new alleles and allelic combinations were characterized, and a molecular analysis in which a cloned genomic DNA fragment containing su(f) was used (in collaboration with Dr. K. O'Hare, Imperial College, London) to determine molecular lesions for the su(f) alleles. Genetic analyses of this locus included complementation studies of su(f) alleles and studies of suppression and enhancement at other target loci. These studies helped us to refine and confirm parts of our hypothesis which we call the Model of Action. The phenotypic effects of suppression and enhancement were proven to be genetically separable. Several new alleles of su(f) were isolated and characterized both molecularly and genetically. These alleles showed a Restriction Fragment Length Polymorphism when probed with the su(f) cloned fragments. These mutational lesions were incorporated into a modified molecular map of this region. Finally, these fragments were shown to hybridize to regions on the salivary gland chromosome that correlate to su(f). Our goal throughout this study was to gain a better understanding of trans-acting gene regulation during normal growth and development.



Digital Repository @ Iowa State University,

Copyright Owner

Cynthia Lynn Fitch-Steenson



Proquest ID


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File Size

156 pages