The increase in publications presenting molecular evolutionary analyses and the availability of comparative sequence data through resources such as NCBI's GenBank underscore the necessity of providing undergraduates with hands-on sequence analysis skills in an evolutionary context. This need is particularly acute given that students have been shown to bring misconceptions about evolution to the classroom, and these misconceptions can hinder their learning about genetic sequences, mutation, and evolutionary processes. However, undergraduate institutions sometimes lack sophisticated analytical software in student computer laboratories. Here we present a computer laboratory exercise utilizing freely available analysis software, and which is designed to analyze sequences that can be obtained from GenBank or other online sources. The exercise is flexible in its complexity, allowing instructors to modify the lab to suit the needs and skills of their classes, and was significantly helpful to introductory biology students in understanding the basics of sequence variation and analysis. (Contains 1 table.)