This multipart activity is designed to give students a firm understanding of genetic profiling using short tandem repeats (STRs), which is a process used by forensic labs around the world.

In Part 1 of this activity, students learn the basics of DNA profiling, including the structure and inheritance of STRs. In Part 2, students learn how DNA profiles are compiled with STRs that are typically used in forensic investigations. In Part 3, they work through a case study involving a robbery and build a DNA profile that can be compared to one constructed from a DNA sample left by a suspect at the scene of the crime. Throughout, analysis questions walk students through calculations on allele frequency and probability (using real data from national databases), providing opportunities for formative assessments of students’ understanding of DNA fingerprinting applications.

This activity can be used on its own or could be followed by downloading and unzipping the accompanying case studies in which students apply what they have learned to solve four cases: 1) twins switched at birth, 2) revisiting evidence from a crime for which the accused was sentenced to life in prison, 3) identifying a missing person, and 4) identifying victims of an earthquake.