Misconceptions of scientific concepts have been believed to be very persistent and difficult to be overcome through regular classroom activities. Therefore, it is important to find the misconceptions and cognitive structure of students. Mendelian genetics is an important and difficult topic for the student to learn. It is also difficult for the teacher to teach. Chromosome theory of inheritance and the concept ~f gene is the most important and difficult topics relate to mitosis/meiosis. The purpose of this research is a study of middle school students` understanding of the physical relationship of chromosome and genes. Particularly, this study is to establish new teaching strategy of the 3rd grade middle school students, by analyzing misconceptions of genetic continuity and to enhance their problem solving performance. Total 100 students were selected for this study from 2 different classes. They were all females. The test taken by students was open ended questionares. It was developed by Moll & Allen(1987) and it was modified far this study. Misconception was analyzed by personal interview. Each of the interviews was recorded and transcribed. Everything that students wrote and drew during the interviews, as well as the interview transcripts, were used to construct the data to be analyzed. The new instruction program $quot;chromosome card game$quot; used to reverse the misconceptions of Mendelian genetics, which were discovered in this study. The new instruction program was reviewed by having controlled, experiment and treated additional study group. The results of this study are as follows: 1. Students have misconception on sister chromatids, the pairs of homologous chromosomes and gate types. 2. According to the conceptual knowledge of chromosome and genre behavior, three types of chromosome model were suggested such as one-chromosome model, two-chromosome model and four-chromosome model. Many students can not construct the conceptual knowledge of genetics and meiosis. There is a tendency toward being mathematical rather than genetic in problem solving. 3. After the new instruction program was applied to the students, much enhanced study effect was discovered among experiment group. Based on above mentioned study, the classroom teachers must. recognize the misconceptions some students have, and modify students` misconceptions, and increase the probability of mearungfu! learning.