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Presentation 1B5. DNA "Fingerprints" and their Statistical Analysis in Human Populations

A. Marie Phillips (Australia)


Presentation Abstract

In 1985 the concept of a "DNA fingerprint" was introduced as a means of evaluating human identity and relatedness. The possible forensic and legal applications of DNA evidence were quickly appreciated and such data are now frequently presented in court cases involving serious crimes such as murder and rape. DNA evidence is also used in establishing paternity, in determining relatedness in immigration and inheritance disputes, and in identifying disaster victims. Such cases, especially those involving famous people, are widely reported in the media and are of interest to the general population. Also, many people will be called to serve on juries in cases where DNA evidence is presented. As statistical concepts are involved in evaluating such evidence, "DNA fingerprinting" as a topic can be used to introduce statistical analysis to undergraduates. If a non-mathematical approach is taken many concepts can be taught to secondary schoolchildren, extending their understanding of statistics while holding their interest with practical " real-life" examples.

There is no doubt that the DNA sequence of each individual is unique, with the only current exceptions being natural clones such as identical twins. However, it is not practical to sequence and compare the total DNA of individual people. Instead, short regions of repeated DNA, STRs (short tandem repeats) or VNTRs (variable numbers of tandem repeats) are analysed and provide the "DNA fingerprint". If there is no match between data the "suspect" is definitely excluded. If there is a match, then the question arises as to what is the probability of a particular data set belonging to more than one individual. In the early 1990's a heated debate occurred between population geneticists regarding the accuracy of such calculated probabilities. At the basis of this argument is the complexity of human populations, and of the interactions between populations.

In this paper we will review some of the questions raised in the debate, and why such data may be best thought of as a DNA profile, or DNA evidence, rather than a "fingerprint".


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