Date of Award

Summer 1-1-2020

Degree Type


Degree Name

Master of Science In Biology Degree


Biological, Geological and Environmental Sciences

First Advisor

Boerner, G. Valentin

Second Advisor

Aaron F. Severson

Third Advisor

Bibo Li


In the process of meiosis, 4 haploid cells are produced from 1 diploid cell in two rounds of division. During prophase I of meiosis I, double strand breaks (DSBs) are created by the Spo11 protein, some of which are later repaired by homologous recombination into crossovers. During homologous recombination, structures called Holliday Junctions are formed, which later are resolved into crossovers to allow homologous chromosomes to separate. Ifthey are not resolved, the cell arrests and cannot progress further in meiosis. I have investigated three proteins known or suspected to be involved in Holliday Junction formation and resolution: the transcription factor Ndt80; the E3 ligase Zip3, and the endonuclease Mlh3, in Saccharomyces cerevisiae, as well as investigating their effects on spore viability and DSB formation. My experiments have lead me to conclude that (1) NDT80, although involved with Holliday junction dissolution, is not involved with their formation, (2) ZIP3 is involved in both formation and resolving of Holliday junctions, (3) MLH3 controls a stage of recombination prior to Holliday Junction resolution, and (4) NDT80 and ZIP3 are involved in nuclear morphology. These findings suggest that NDT80, ZIP3, and MLH3 have much broader roles than previously assumed.

Included in

Biology Commons