We investigate the effects of antisymmetrization with respect to valence quarks in nuclei introducing "quark exchange currents". Their effects in ordinary nuclei are found to be small for lack of contribution from s-wave nucleon pairs owing to spin-isospin symmetry. For example, the Gamow-Teller type β-decay matrix elements for A = 15, 17, 39, 41 and ∞ nuclei are reduced from the single-particle values by 2-8% depending on the baryon size. The effects seem to be larger for Σ-hypernuclei. For example, the magnetic moment of Σ +4Li(1 +) is reduced by more than 15%. For Λ-hypernuclei, however, the effects on the magnetic moments tend to cancel each other, and about 1% reduction is obtained for 4ΛHe(1 +).