Abstract: This study aimed to determine the level understanding of students, who experience the misconceptions, know the concept and do not know the concept of genetics; sub concepts which often become a misconception and the factors that cause the occurrence of misconceptions. This study used CRI method (Certainty of Response Index) to identify the students’ misconceptions. The population in this study are the Biology Department. The sample as the subjects in this research are the Biology Department students of Makassar State University period 2011 with 91 total numbers consisting of two classes; class ICP (International Class Program) and class A educational study program. The instrument used was diagnostic tests in form of reasoned multiple choice equipped with CRI value and a structured interview to find out the cause of the misconceptions. The findings showed that there was a misconception on eight sub concepts which was observed by the percentage experiencing misconceptions, understanding the concept and not understanding the concept in succession 45.8, 28.2 and 26%. The highest percentage of the students experiencing misconceptions contained in the sub concepts of Mendel inheritance 60.2%, sub concepts of protein synthesis 59% and sub concepts of mutation 55%. Factors becoming the cause of misconceptions were the wrong understanding to the concept, the incompleteness information received from the students, the wrong experiences and observations of the students, the terms and concepts that have been so long, learning experience at school and errors in the textbooks.