DRD4 Allele Frequency as a Lab Exercise in Neuroscience and Genetics Courses

DNA segments with variable number tandem repeats (VNTR) serve as a model for students to learn DNA extraction and polymerase chain reaction (PCR) techniques in biology laboratory courses from the high school to the graduate level. Because of a growing interest in the neurosciences among undergraduates, we have developed a PCR exercise with a focus on the nervous system and behavior, with the aim of inspiring students from all aspects of the neurosciences to appreciate the central dogma and neurogenetics. DRD4 was a good candidate to provide a lab exercise that would be more engaging than VNTR analysis of a non-coding segment. DRD4 encodes for the dopamine D4 receptor and has been controversially associated with 'novelty seeking' or 'wanderlust' behavior. DRD4 has three common variants of the 48 bp sequence on exon 3, easily differentiated through gel electrophoresis. The 2 repeat (2R), 4 repeat (4R) and 7 repeat (7R) of the 48 bp sequence are the most common alleles. The 7R sequences result in the expressed dopamine D4 receptor having less affinity for dopamine binding, which was proposed to be the reason individuals engage in 'novelty seeking' behavior, to increase dopamine release to facilitate more binding to the receptor. Here we demonstrate an enjoyable and simple two lab sequence to analyze DRD4 genotypes that is appropriate for neuroscience and genetics courses.