Using the Genetics Concept Assessment to document persistent conceptual difficulties in undergraduate genetics courses.

To help genetics instructors become aware of fundamental concepts that are persistently difficult for students, we have analyzed the evolution of student responses to multiple-choice questions from the Genetics Concept Assessment. In total, we examined pretest (before instruction) and posttest (after instruction) responses from 751 students enrolled in six genetics courses for either majors or nonmajors. Students improved on all 25 questions after instruction, but to varying degrees. Notably, there was a subgroup of nine questions for which a single incorrect answer, called the most common incorrect answer, was chosen by >20% of students on the posttest. To explore response patterns to these nine questions, we tracked individual student answers before and after instruction and found that particular conceptual difficulties about genetics are both more likely to persist and more likely to distract students than other incorrect ideas. Here we present an analysis of the evolution of these incorrect ideas to encourage instructor awareness of these genetics concepts and provide advice on how to address common conceptual difficulties in the classroom.