Degree Type


Date of Award


Degree Name

Doctor of Philosophy




Controlling elements have the ability to activate and deactivate standard genes. One of the unique features of controlling elements is their ability to transpose from one position along the chromosome to another. In this study, the transposition of the controlling element En was examined within the distal two-thirds of the 3L maize chromosome arm;Stable germinal mutations representing losses of En were selected from three autonomously mutating al alleles. The insertion of En at a new location was confirmed by crosses of the stable mutants to responsive tester lines. The position of En at the primary transposition site was determined by backcrossing to an al et line using standard three-point tester lines. Secondary transpositions were detected by Chi-square comparisons of progeny to parental En linkage studies;Although En positions were found throughout the segment of chromosome examined, their distribution was not random and some regions of the chromosome were more likely to contain an inserted En. En's from all three autonomously mutating source alleles showed the same regional preferences and distributions of transposed En's from the three alleles were not significantly different in Chi-square tests. Both primary and secondary sites of insertion were located within these regions. No differences were found between the distribution of primary sites of insertion and the distribution of secondary sites;The difference in En transpositional activity within different chromosomal regions may be due to the replication patterns of the maize DNA or to the percentage of A-T base pairs within these regions. Correlations between the pattern produced by En on a standard allele and the En position were also examined. While an association between transposition and pattern change was observed, no correlation between pattern and linkage position was found.



Digital Repository @ Iowa State University,

Copyright Owner

Elaine Maytag Nowick



Proquest ID


File Format


File Size

115 pages