A model for two functionally distinct populations of dynein at the embryo cortex. DHC-1, LIN-5, and DNC-1 are necessary for MT gliding behavior and generate force by pulling on MTs that contact the cortex at shallow angles (θ1), contributing to pronuclear centration (left; blue text). DHC-1, LIN-5, and members of the heterotrimeric G protein pathway are necessary for normal anaphase spindle-pulling forces (right), but many of these components did not significantly alter MT gliding behavior (black text). Because most MTs contact the cortex at orthogonal angles in the one-cell metaphase/anaphase embryo (θ2), anaphase force likely occurs primarily through end-on interactions (right). The two mechanisms proposed are shown to reflect relative contributions and are not necessarily mutually exclusive.