05 - Biotechnology Basics: My First Electrophoresis
Scenario B: Crime Scene Investigation Using SYBR® Safe Stain In this scenario, students will analyze PCR reactions obtained from 3 different sus - pects and compare them to a crime scene sample. In humans, DNA is packaged into 23 pairs of chromosomes that are inherited from an individual’s biological parents. Although most of this genetic material is identical in every person, small differences, or “polymorphisms”, in the DNA sequence occur throughout the genome. For example, the simplest difference is a Single Nucleotide Polymorphism (or SNP). Changes in the number and location of restriction enzyme sites result in Restriction Fragment Length Polymorphisms (or RFLPs). Short repeti- tive stretches of DNA at specific locations in the genome can vary in number to produce STRs (Short Tandem Repeats) and VNTRs (Variable Number of Tandem Repeats). Although most polymorphisms occur in non-coding regions of DNA, those that disrupt a gene can result in disease. Medical diagnostic tests can identify specific polymorphisms associated with disease. Analyzing several different polymorphisms within a person’s genome generates a unique DNA “fingerprint”. DNA fingerprints can allow us to distinguish one individual from another. Because polymorphisms are inherited, DNA fingerprints can also be used to determine paternity/maternity (and other familial relationships). The best-known application of DNA fingerprinting is in forensic science. DNA fingerprint - ing techniques are utilized to interpret blood, tissue, or fluid evidence collected at accidents and crime scenes. After DNA is extracted from these samples, forensic scientists can develop a DNA fingerprint. The DNA fingerprint from a crime scene can then be compared to the DNA fingerprints of different suspects. A match provides strong evidence that the suspect was present at the crime scene.
Lane 1 2 3 4 5 GEL LOADING For Scenario B - Crime Scene Tube Sample Tube A DNA Standard Marker Tube B Crime scene PCR reaction Tube C Suspect #1 PCR reaction Tube D Suspect #2 PCR reaction Tube E Suspect #3 PCR reaction
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