A hands-on instructional approach with medium-achieving 10th-grade students (N = 294) successfully demonstrated the achievement of a conceptual change. Two teaching variations were applied (I-1, I-2), both dealing with a hands-on gene technology lesson in an out-of-school laboratory. I-2 additionally confronted the participants with alternative conceptions to some of the central issues involved in gene technology following a constructivist teaching model. The authors monitored the percentage of alternative conceptions by pretest, posttest, and delayed posttest. In the long term, I-2 abandoned more of students' alternative conceptions in favor of the orthodox scientific view. Furthermore, a gender effect appeared: In the short term, more young men within I-2 were forced to shift to more scientific conceptions. Young women filed their alternative conceptions also in the long term, independently of the applied instructional method. (Contains 6 tables and 2 figures.)