All junior high school science textbooks in Japan include a cautionary statement that dominance and recessiveness in genetics do not equate to superiority and inferiority. However, no surveys have been conducted in Japan with the intent of revealing how many students possess misconceptions on this topic, and accompanied by exercises intended to correct their false perceptions. In this study, we implemented a survey of students’ recognition accompanied by exercises concerning dominant traits. The participants were third-year students in two junior high schools. The results showed that some of the surveyed students thought dominant traits were advantageous for survival. We also found our exercises were effective for correcting such misconceptions.

Annealing of the primers to the template DNA in PCR is poorly described in authorized high school biology textbooks. After a regular class in which textbooks were used, none of the students could precisely estimate the length of the amplified DNA fragment. A worksheet with an illustrated description of the PCR and an exercise for the estimation of the amplified fragment length was prepared to emphasize complementary combination of the primer and the template DNA. Moreover, the students had a brief practice of micropipetting to perform a PCR accurately. We conducted an experimental teaching using this worksheet, and the effectiveness of the worksheet was subsequently determined. After teaching students using the worksheet, 65% (n = 20) of class could correctly estimate the length of the amplified DNA fragment. This result shows that a detailed description was required for students to successfully understand the principle of the PCR.