Concept Introduction
The students will be directed
to the website: http://www.vivo.colostate.edu/hbooks/genetics/medgen/dnatesting/
The students will be directed to read the following website to reinforce their understanding of the processes involved in using DNA evidence in a criminal trial and to get a different perspective on DNA fingerprinting: http://www.scandals.org/articles/pk021019.html
To
further build upon their previous lesson of Heredity, the students will review
the following website to tie this lesson and the previous lesson together:
The focus of most criminal investigations is on linking evidence from the crime scene to suspects, and for more than a century, science has played an increasingly important role in this process. Fingerprinting was applied to criminal investigations beginning in the 1880's. Shortly after the principle of ABO blood typing was reported in 1900, its relevance to forensic investigations became apparent. In the 1960's human leukocyte antigen (HLA) typing became the premier serologic tool for personal identification, although in practice, it was useful for only a small percentage of samples.
Finally, the 1980's ushered in the age of DNA testing, which permits investigators to perform almost unbelievable feats of identification. With current techniques, it is possible for a single person to be differentiated from all the people that have ever lived using DNA from a single hair root.
The principles and techniques used for forensic DNA typing are also quite useful for other purposes. DNA profiles are widely used in resolving issues of parentage in man and animals, and are rapidly replacing serologic analysis (i.e. blood typing) for that purpose. Additionally, DNA testing is an indispensable tool for positional cloning, a technique by which a previously unknown gene is identified by finding associations or links between DNA markers and the inheritance of a disease.
The purpose of DNA typing in forensic medicine is to match a sample from the crime site with a suspect. Technically, application of the techniques described above do not actually determine whether the sample came from the suspect. Rather, statistical analysis of the test results yield a probability that the sample did not come from the suspect, and with DNA typing, that probability can be so miniscule as to be certain. Importantly, DNA testing has proven to be as powerful for exonerating suspects as it has for convicting them. Indeed, about one in three cases reported by FBI laboratories, DNA testing proved that the current suspect could not have committed the crime, which in many cases was followed by apprehension and conviction of the true perpetrator.
A great diversity of criminal detection has benefited from DNA testing, and it has been especially valuable in solving rape and murder cases. Additional examples include robbery, assault, kidnapping, car accidents, extortion and blackmail. It also has been successfully applied to parentage determination and useful in settling certain immigration disputes that hinges on proving family relationships.