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biology, mutants, cell division cycle, kluyveromyces lactis, genes


Biology | Cell and Developmental Biology | Genetics and Genomics | Life Sciences


The cell division cycle is the process by which all cells grow and reproduce. Mechanisms underlying the control of this complicated process have been studied at great length, but are not completely understood. Proper timing and sequencing of events in the cell cycle are maintained by gene products (Morgan, 2007). These Cdc (cell division cycle) proteins perform specific cellular functions that will promote transitions in the cell cycle depending on the current conditions of the internal and external environment. It is important to isolate and identify the function of CDC genes in order to understand how a normal cell cycle works, and how to fix it if it malfunctions. An ideal subject for studying the cell cycle in eukaryotes is budding yeast.

Currently, our lab has identified ten cdc mutants using a temperature sensitive (ts) and cdc screen in the budding yeast K. lactis that fall into eight complementation groups. Several additional strains of K. lactis have been identified as potentially carrying cdc mutations in new CDC genes not yet identified. The project discussed in this thesis sought to confirm that these strains were cdc mutants through a new cdc screen. Afterwards, a backcross of the newly identified cdc mutants was performed to create diploids for a recessiveness test and tetrad analysis. Two cdc mutant strains, RCY1110 and RCY1124, were found to carry recessive genes. After several tetrad analyses of these two strains, each was found to only contain a single mutated gene. The ts gene in RCY1110 displayed possible linkage to URA3, while the ts gene in RCY1124 displayed possible linkage to ADE1. Cells from the RCY1110 strain have no bud upon arrest, while cells from the strain RCY1124 exhibit a large bud upon arrest. In future, these mutant strains can undergo complementation testing before the final step of identifying the mutated gene with cloning by complementation. Several other strains including RCY1120 and RCY1123 were found to exhibit Cdc phenotype, but analysis was discontinued as they were found not to be ts on solid media. One strain, RCY1126, was concluded to deviate from the usual bud morphology, but could not be categorized as a cdc mutant because there was no uniform arrest of the cells. RCY1126 and the apparent non-ts strains would be interesting strains to study in a future investigation.

Department 1 Awarding Honors Status


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This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License