The grown-in dislocation dynamics and interaction mechanisms with growth twins are investigated in-situ during the directional solidification of silicon crystal. The melting, solidification and cooling down process is performed in a dedicated installation at the European synchrotron radiation facility and is followed by X-ray Bragg diffraction imaging techniques (X-ray topography) at the mesoscale in real-time. Existing dislocations in the seed are observed to propagate in the up-grown crystal via replicas. They expand vertically with the moving solid-liquid interface being always aligned perpendicular to the growth front. During the solidification process when they meet a growth twin lamella (Σ3{111}), they neither pile-up nor transmit through the boundary. They are blocked by the twin, but they continue to move laterally behind the growth front due to the thermomechanical stresses in the system. The existence of dislocations at the solid-liquid interface, their evolution and interaction with twin boundaries is discussed, as growth proceeds, based on a detailed crystallographic analysis of the system.