PCR in Forensic Science: DNA Fingerprinting

Students will amplify their own cheek cell DNA from a saline mouthwash and then PCR amplify their D1S80 locus. Following PCR, students will electrophorese their PCR products on TBE polyacrylamide gels. This allows for better separation of the D1S80 alleles, which differ by 16 bp, and exposes students to another method of electrophoresis.

After staining and photographing their gels, students will be ready for analysis. First, students will use a 50 bp DNA ladder of molecular weight markers to generate a standard curve. They will measure the distance each band in the marker lane migrated from the well and will then calculate the log of that distance. Using a graphing calculator, students will plot their “X” values (the log of the distance each band migrated) and their “Y” values (the corresponding size of each band in the 50 bp marker).¬†After measuring the distance their allelic band(s) traveled, students will use linear regression to determine their allele size(s).

Intermediate to Advanced: This lab follows real-life analysis or DNA fingerprinting and is also flexible depending on the teacher and students. The laboratory portion is intermediate as it introduces a different type of gel electrophoresis, while the concepts and mathematical analysis are advanced. This lesson is appropriate for biology, criminal justice or law, and biotechnology courses.

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gretchen@18east.comForensic Analysis of DNA Samples