DNA Profiling

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Since the first use of DNA profiling in 1985, the process has seen extensive use in the fields of forensic science and genomics. DNA profiling is a technique predominantly used in forensic science, to identify individuals based on the unique characteristics of their DNA. DNA profiling was developed in 1984 by Sir Alec Jeffreys (see Fig. 1), when he noticed that certain sequences of highly variable DNA which were non-coding, were repeated within human genes (McKie, 2009). With this discovery, he recognised that each individual has a unique pattern of non-coding DNA sequences.

With the application of this technology, forensic scientists have been able to; reduce the number of wrongful arrests, increase the reliability of criminal evidence,
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Sufficient quantities of DNA are different enough, that it is possible to distinguish one individual from another, unless they are identical twins (Better Health Channel, 2015). DNA profiling looks at the non-coding regions (aka “junk sequences”) of DNA that are highly variable, called Variable Number Tandem Repeats (VNTRs). In the process of DNA profiling, forensic scientists compare these variable regions of DNA that are unique to each person.

Modern technology has shown that the probability of someone having the same DNA profile as another individual, is one in 1018 (Easteal & Easteal, 1990).

Currently, short tandem repeats (STRs) are utilised for identification purposes. Similar to VNTRs, STRs are more durable, last longer and are more resistant to DNA degradation due to their smaller size (Easteal & Easteal, 1990). An image of STRs gathered from gel electrophoresis is shown on the pervious page (Fig. 2). The following image is a diagram of the process behind performing a DNA
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Of these cases, 41% yielded a positive result that helped to identify a suspect, when the DNA profile had been uploaded and used to search the DNA database of prior offenders (Johns & Rushing , 2009).

Where DNA profiling had been integrated into investigative procedures, suspects were identified more than two and a half times more frequently than when only traditional investigative methods were used (see fig. 4). Arrest and conviction rates also doubled, for crimes in which biological evidence was identified (Johns & Rushing , 2009).

It was found that DNA profiling has had a profound effect on the crime rates of burglary in Denver, USA. Prior to the introduction of the technique, property crimes in Denver had increased at a consistent rate of 5% each year. Since the technique’s introduction, burglary rates have dropped by 26% (Johns & Rushing ,