Identifying Human Remains
Human remains are fascinating. They have many properties that can be used to identify a person: distinct scars, special features, dental x-rays, fingerprint comparisons, or physical facial characteristics. Forensic scientists attempt to identify human skeletal remains in situations like mass fatality incidents involving military personnel or others recovered from war, fires, explosions, and in criminal matters. However, bodies may degrade faster depending on environmental conditions like climate, bacterial growth, insects and scavenger animal presence. Because extensive putrefaction or destruction of the remains may occur, the preferred tool would be DNA typing: a powerful tool for identifying human remains (Shaler, 2002).
One of the greatest challenges when attempting to identify victims of mass fatality incidents is analyzing DNA from bone (Holland et al., 2002; Lawler, 2001). Bone is more difficult to extract DNA from. Sample quantity recovered may be too small to properly isolate sufficient amounts of DNA. To obtain an adequate quality and quantity of DNA templates, strategies to improve the yield of DNA isolation are needed. Below is a simple sample processing method for DNA isolation that provides an alternative to the gritty cleaning method of sanding that ensures quality sample.
Bone samples may be compromised in mass fatalities, like the attack on the World Trade Center.
Processing Bone Samples – Time and Labor Intensive
Cleaning and sampling of the bone can be a labor-intensive and a time consuming step, but it is required prior to isolating DNA from bone samples. The outer surface of the bone fragment must be cleaned by using a physical method, such as sanding, to avoid contamination by physical contact, environment-borne inhibitors, and bacterial contamination, all of which may interfere with forensic DNA analysis. Avoiding cross-contamination between samples is also necessary, so the bone dust generated by sanding the bone must be cleaned and removed. Special safety protection equipment and procedures are also needed to protect laboratory analysts from exposure to blood-borne pathogens. Since the sanding method is difficult to be adapted for automation, a simple processing method using trypsin solution was developed (Li et al<, 2009).
Trypsin Can Be Used to Clean Bone
Trypsin is a protease secreted in the digestive system to break down proteins, a process known as proteolysis. Trypsin was chosen because it can degrade various types of proteins (Buck et al., 1962; Walsh, 1970). It has been used in enzymatic maceration methods for processing bone samples in anthropological laboratories (Hangay and Dingley, 1985; Hendry, 1999). In a previous study, the trypsin maceration technique was adapted to the sample processing method prior to DNA isolation from bone samples.
Image from (Li, 2009)
The soft tissue and outer surface of the bone fragment samples can be removed using a trypsin treatment. Our data suggests that this method can be used in the initial sample preparation for cleaning the outer surface of human bone samples prior to DNA isolation. In another study, the application of the sample processing method for DNA isolation was further evaluated: 1) the effect of trypsin treatment on DNA yield, and 2) the effect of trypsin treatment on the quality of DNA isolated.
Image from (Li, 2009)
With the help of the protease trypsin, the hazards involved in cleaning bone are lessened, removing exposure to blood-borne pathogens and physical safety risks. The use of trypsin as a sample cleaning agent has shown the effectiveness of proteases as helpers in scientific endeavors, especially in assisting DNA extraction.
- Li, R. (2009). Application of Proteinases for DNA Isolation of Bone Specimens.