Required for chromosome movement and orientation on spindle poles in mitosis and meiosis (PubMed:15452142). May play a role in early anterior-posterior chromosome movement in mitotic embryos (PubMed:15452142). Localizes to nuclei of the distal mitotic zone (PubMed:15452142). During mitotic prophase in embryos, localizes to the nucleoplasm (PubMed:15452142). In prometaphase, localizes to the body of the spindle and the periphery of chromosomes (PubMed:15452142). In anaphase, localizes to the spindle interzone (PubMed:15452142). Localizes to early meiotic prophase nuclei and to the nucleoplasm in late prophase (PubMed:15452142). Localizes to prophase chromosomes before fertilization (PubMed:15452142). During metaphase of meiosis I and meiosis II, localizes to the body of the spindle, around the periphery of chromosomes, and between homologous chromosomes (PubMed:15452142). Expressed in the gonad. Expressed in embryos. RNAi-mediated knockdown results in embryos that undergo early mitotic divisions as in wild-type, but which later then display aberrant patterns of nuclei and arrest before morphogenesis (PubMed:15452142). RNAi-mediated knockdown results in chromosome segregation defects in mitotic embryos whereby chromosomes form a disordered metaphase plate and multiple chromosomes exhibit delays in segregation resulting in the formation of bridges during anaphase (PubMed:15452142). The chromosome bridges stretch, break and sometimes form micronuclei (PubMed:15452142). RNAi-mediated knockdown results in kinetochore orientation defects in anaphase spindles in embryos in which kinetochores do not align on the spindle and some kinetochores stretch across the spindle interzone, parallel to the pole-pole axis (PubMed:15452142). RNAi-mediated knockdown does not cause defects in spindle architecture or cytokinesis in embryos (PubMed:15452142). Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Kinesin family.