Asymmetric cell division is the unequal segregation of cell fate determinants into daughter cells following mitosis. In addition, some asymmetric divisions lead to daughter cells of unequal sizes. The regulation and functional significance of the unequal daughter cells size are unknown. To investigate this, we are using the bristle pattern in the adult fruit fly, which arises in the notum (dorsal thorax) during pupariation. The sensory organ precursor (SOP) cells undergo a series of asymmetric divisions to give rise to the cells of the mecahnosensory organ. During the first division, cell fate determinants, Numb and Partner of Numb localize to the anterior cortex, while Bazooka localizes to the posterior and each segregates into the anterior and posterior daughter cells respectively. In addition, the resulting daughter cells are of unequal sizes, a larger posterior cell and a smaller anterior cell. Chromosome passenger complex (CPC) are a complex of proteins, that localize early in mitosis to the kinetochores. During anaphase, they move from the kinectochores to the spindle midzone, and specify the position of the future cleavage furrow. Owing to their dynamic localization pattern during mitosis, we are investigating their role in the asymmetric SOP divisions. Additionally, using genetic tools, we aim to perturb the daughter cell size and the relative size of the cells to determine the significance of cells size during lineage specification.