Living organisms are composed of cells; thus, cells are called the basic building blocks of life. In order for an organism to grow, cells undergo mitosis. During mitosis, chromosomal DNA is replicated and segregated into two daughter cells. Errors in segregation can lead to the development of some forms of cancer. Because of this, equal chromosome segregation is a critical mitotic process. Microtubules are fibril-like cytoskeletal structures that are responsible for chromosome separation. They originate from two centrosomes. The growth and extension of microtubules push the two centrosomes apart, creating two poles in a mitotic cell. Kinetochores bind to these microtubules and align at the center of the cell. Disassembly of these microtubules is coupled to the equal segregation of sister chromatids. In Saccharomyces cerevisiae, correct kinetochore-microtubule attachment is mediated by the Ndc80 and Dam1 complexes. The heterotetrameric and rod-like Ndc80 complex is the main microtubule-binding component of the kinetochore. The heterodecameric Dam1 complex forms oligomeric rings around microtubules and enhances the microtubule-binding capacity of the Ndc80 complex. In vitro, the Ndc80 complex bridges two Dam1 complex rings, yielding a specific 33 nm inter-ring distance. To investigate the importance of this distance, we constructed various mutant Ndc80 complexes to further increase the Dam1 complex inter-ring distance. Specifically, each Ndc80 complex mutant contained an 8, 10, or 12 heptad repeat insertion that elongated the length of the coiled-coil domain of the Ndc80 complex by 8, 10, and 12 nm, respectively. We tested if these mutant Ndc80 complexes support cell division by transforming a yeast strain that does not contain wild-type Ndc80 gene and selecting for growth on SD-ura low adenine plates. These produced non-sectoring red colonies; therefore, the constructs did not support cell division. This suggests the specific 33 nm Dam1 complex inter-ring distance is important for cell viability.