In this lab your instructor will explain a crime scenario that has taken place in the MS building. You will be presented with evidence that will be tested for the presence of blood and DNA fingerprinting will be conducted.
Human blood or blood products are not used in any MCCC laboratories. Sheep blood which is purchased sterile and free of antibiotics and preservatives is used to generate blood stained materials. Dye compounds will be used to mimics the response of DNA fragments subjected to gel electrophoresis.
Blood detection using the Kastle-Meyer test
The Kastle-Meyer test is a quick inexpensive test used to analyze evidence at a crime scene for the presence of blood. Phenolphthalein reacts with hydrogen peroxide in the presence of hemoglobin to turn from colorless to pink. This reagents provide a presumptive test for blood, as food samples which contain hemoglobin (meat) and certain vegetables will also generate a positive response. An additional benefit of this procedure is that the samples remain intact and can be used in further testing including DNA analysis.
- Swab evidence with a dampened cotton swab
- Add swab to test tube containing about 1 cm of distilled water, swish to release contents.
- Add several drops of Kastle/Meyer reagent.
- Add several drops of hydrogen peroxide.
- A positive result will give a bright pink color.
Based on the scenario described by your instructor, enter a description of the 2 pieces
of evidence and indicate if the samples were positive or negative for blood residue.