A Molecular Biology-Based Practical Examination Used in a Capstone Laboratory Course for Biochemistry Majors

Abstract

A hands-on summative assessment was developed in a capstone laboratory course for biochemistry majors to evaluate students' ability to independently execute several molecular biological techniques simultaneously. These techniques included plasmid DNA quantification, assembling a series of restriction enzyme (RE) digests, loading an agarose gel, electrophoresis, imaging the resultant RE digest fragments, and finally, using deductive reasoning to interpret the banding pattern to draw a well-labeled restriction fragment map. A 3-page prompt was sent to students 48 hours prior to coming to the practical examination to provide time to prepare tables and protocols to successfully execute the experiments necessary for the restriction fragment map construction. Students were provided with a 200 ng aliquot of the pBR322 plasmid of unknown concentration. After using a Qubit fluorometer to determine DNA concentration students were told to use XmnI and BamHI REs to digest the plasmid and to save at least 40 ng of the original unknown plasmid aliquot to load on the agarose gel. Students were not told the exact identity of the plasmid nor were they told how many restriction digests to perform. The average time to complete this practical was approximately 3 hours and all students achieved interpretable gel image results. This exam was developed as an alternative to enzyme kinetics-based exams typically used in the same course for many years. All reagents necessary for this exam are commercially available making it easily adoptable.