The purpose of this study was to investigate primary students' learning through participation in an out-of-school enrichment programme, held in a science centre, which focused on DNA and genes and whether participation in the programme led to an increased understanding of inheritance as well as promoted interest in the topic. The sample consisted of two groups (245 students in the experimental group and 150 students in the control group) of upper primary students (Grade 5) from six schools in Singapore. Two instruments were developed--a 15-item multiple-choice test to measure learning gains and a 17-item survey form to measure student feedback. Pre-, post-, and delayed post-tests were administered. Results showed statistically significant gains in learning for the experimental group that appeared to be stable as well as high levels of interest stimulated by the programme. (Contains 8 tables and 1 figure.)