vector: (genetics) a virus or other agent that is used to deliver DNA to a cell
virus: (virology) ultramicroscopic infectious agent that replicates itself only within cells of living hosts; many are pathogenic; a piece of nucleic acid (DNA or RNA) wrapped in a thin coat of protein
precession of the equinoxes: a slow westward shift of the equinoxes along the plane of the ecliptic caused by precession of the Earth's axis of rotation