DNA fingerprint analysis of three short tandem repeat (STR) loci for biochemistry and forensic science laboratory courses

We have devised and implemented a DNA fingerprinting module for an upper division undergraduate laboratory based on the amplification and analysis of three of the 13 short tandem repeat loci that are required by the Federal Bureau of Investigation Combined DNA Index System (FBI CODIS) data base. Students first collect human epithelial (cheek) cells using sterile buccal swabs and then utilize commercially available kits and materials to extract genomic DNA. This is followed by the PCR amplification of three specific short tandem repeat loci (i.e. CSF1PO, TPOX, THO1). Polyacrylamide gel electrophoresis is used to resolve the allelic bands associated with the three short tandem repeat loci, and the results are statistically analyzed in the context of human population genetics. In addition, DNA was collected from a family, and the children's allele sets were compared with those of the parents to help illustrate paternal and maternal relatedness. This module enables students to use the materials and methods employed by actual law enforcement agencies and therefore can be used for laboratory exercises in traditional biochemistry curricula as well as for the growing field of forensic science and education.