Kit Summary This kit allows students to conduct real-world forensic DNA analyses and introduces them to the techniques and applications of PCR and gel electrophoresis. As crime scene investigators, students will use PCR and agarose gel electrophoresis to analyze the genotypes of several DNA samples – one obtained from a hypothetical crime scene and four from hypothetical suspects. • • •
Lesson 1: Set up polymerase chain reactions (PCR) Lesson 2: Electrophoresis of PCR products Lesson 3: Gel drying and analysis of results
Reagents for gel electrophoresis are available as separate modules; see the kit inventory (page 2) for more information. The Crime Scene Investigator PCR Basics™ kit provides all necessary reagents (primers, template DNA, and Taq polymerase) for students to perform the PCR. After performing PCR, students use electrophoresis to analyze the DNA samples and identify the genotypes using a reference allele ladder. They then match one suspect's DNA sample to the DNA collected at the scene of the crime. Following DNA profiling of a single genetic "locus", the teacher has the option of an additional teaching experience that simulates the use of the 13 core loci used in actual forensic casework. This simple exercise demonstrates the concept of increasing power of discrimination with increasing numbers of loci typed, and illustrates how even siblings can be discretely identified by DNA profiling. Each student team will generate their own set of genotypes, collect and record data on a worksheet, and perform simple statistical calculations. Note: The reagents provided in this kit only simulate forensic testing. They cannot be used to perform actual genotyping, and as such do not reveal any information about individual genotypes. Small DNA fragments from 200 to 1000 base pairs are generated in this experiment. To resolve these bands adequately requires a high percentage (3%) agarose gel.
Storage Instructions Place the reagent bag at –20°C within 1 week of arrival. The other reagents can be stored at room temperature.
Intended Audience This kit is appropriate for students who have little or no experience with molecular biology or PCR, but may also be suitable for more advanced students with an interest in the details of DNA profiling, forensic science, and statistics. Students should have an understanding of the following concepts to fully appreciate the kit: • • • • • •
The structure of DNA Genotypes and genotyping Heredity and the passage of genetic information from parents to offspring DNA replication and PCR Cell structure and the storage of DNA within the nucleus Pattern matching and discrimination
Much of this background information is provided in the instruction manual and the appendices. Additional information can be found in textbooks or web sites referenced in Appendix H.
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