Two Major Breakthroughs In Molecular Biology: DNA Fingerprinting

Nowadays, DNA is a crucial component of a crime scene investigation, used to both to identify perpetrators from crime scenes and to determine a suspect’s guilt or innocence (Butler, 2005). The method of constructing a distinctive “fingerprint” from an individual’s DNA was first described by Alec Jeffreys in 1985. He discovered regions of repetitions of nucleotides inherent in DNA strands that differed from person to person (now known as variable number of tandem repeats, or VNTRs), and developed a technique to adjust the length variation into a definitive identity marker (Butler, 2005). Since then, DNA fingerprinting has been refined to be an indispensible source of evidence, expanded into multiple methods befitting different types of DNA

From cases such as OJ Simpson to Chandra Levy, DNA profiling also called DNA fingerprinting or DNA typing has played a major role in the criminal justice system. The law enforcement community uses DNA profiling to rule out or identify suspects. Unlike hair microscopy, bite mark comparisons, shoe print comparisons, and firearm tool mark analysis, DNA typing has been developed through massive scientific research and has undergone meticulous scientific evaluation (Innocence Project). DNA is a foolproof method of identifying a perpetrator of a crime.

(PCR), which isolates small fragments of DNA that have a high degree of variability from

Beginning in the mid-1980s, the development of DNA analysis technology has revolutionised the field of forensic science within the criminal justice system. As the refinement of procedures and technology continues, even minute samples of biological material (including blood, saliva, semen and skin cells) are able to be analysed and used to link or acquit perpetrators of crimes. (Whitney, R n.d.)

DNA testing is a critical and accurate tool in linking accused and even convicted criminals for crimes, and should be widely used to assess guilt or innocence before jail sentences are imposed. It was started up by scientists Francis C. Crick and James D, Watson in 1953 as they had described the uses, structures and purpose of the DNA “deoxyribonucleic acid” genetic fingerprint that contains organism information about an individual (testing

(c) DNA fingerprinting could be used to exonerate or to convict suspected criminals. DNA fingerprinting could also be used to build phylogenetic trees

Due to the uniqueness of DNA it has become a powerful tool in criminal investigations

DNA forensics can also narrow down suspect pools, exonerate innocent suspects, and link crimes together if the same DNA is found at both scenes. However, without existing suspects, a DNA profile cannot direct an investigation because current knowledge of genotype-phenotype relation is too vague for DNA phenotyping. For example, a profile from a first time offender that has no match in any database may give the information that the criminal is a left handed male of medium stature with red hair and freckles. It would be impossible to interview every man who fits that description. However, with available suspects, DNA forensics has many advantages over other forms of evidence. One is the longevity of DNA. Although it will deteriorate if exposed to sunlight, it can remain intact for centuries under proper conditions (Sachs, 2004). Because DNA is so durable, investigators can reopen old cases to reexamine evidence.

Identification means the steps needed in the analysis of unknown fluids to see what the substance is (“Biology,” 2016). Individualization determines whether a certain individual may or may not be the donor of a bodily substance by examining various markers (“Biology,” 2016). Processing biological trace evidence uses highly complex, automated technology to create a DNA profile that helps the investigators through the association of suspects to victims and to crime scenes (“Biology Services,” 2017). By using techniques such as polymerase chain reaction (PCR), forensic biologists can use variable markers found on the regular chromosomes (STR’s), the sex chromosomes (Y-STR’s) and within the mitochondrial DNA to distinguish one person’s DNA from another to a high degree of certainty (“Biology,” 2016). Forensic biologists are involved in assisting investigative agencies because police were led to Bernardo by a police sketch (“Serial Killers: Paul Bernardo and Karla Homolka,” 2013). The police took DNA (hair, blood and saliva) from Bernardo as a matter of routine to test it against specimens found on a rape victim’s clothing (Butts, n.d.). Forensic biologists were able to name the substances left on Kristen French’s body and match it to Bernardo’s DNA by processing it. On February 17th, 1995, Bernardo was arrested for the murders of Mahaffy, French, and the Scarborough rapes (Butts,

able to solve a crime (Smith, 2004). DNA samples identify suspects but one of the more

The results in this lab showed that suspect 2 was a match for the DNA found at the crime scene. This was determined by DNA fingerprinting. In this lab, the samples of DNA from two suspects and the DNA from the crime scene were cut with two different restriction enzymes and then the DNA was run through gel electrophoresis. The different restriction enzymes cut the DNA in different places, so when the DNA was run through the gel, the gel showed two fragments for each sample based on their size. The fragments shown are known as bands of DNA. These bands of DNA for each suspect were analyzed and compared with the bands of the DNA from the crime scene. The bands of DNA were compared based on the distance they traveled through the gel from the wells.

DNA profiling technologies have had a considerable impact on how forensic science and criminal investigation have been understood, carried out, and regulated in the last 25 years. Current methods of forensic DNA profiling (known also as DNA fingerprinting and DNA typing), based on Polymerase Chain Reaction (PCR) amplifications of a varying number of Short Tandem Repeat (STR) loci found at different locations on the human genome, are regularly described as constituting the “gold standard for identification” in contemporary society. Prior to the implementation of PCR based extraction and amplification methods in the 1990’s, the initial uses of DNA fingerprinting (based on Multiple and Single Locus Probes) were largely confined to reactive

DNA fingerprinting was discovered by Professor Sir Alec Jeffreys from the University of Leicster. After spending time studying molecular biology in Amsterdam with Dick Flavell, Jeffreys moved to the university and set out to “marry the new

Law Enforcement keep notes on arrests that have founded people innocent of crimes, and retention of an innocent person's DNA can be charge or otherwise, seen as a invasion of that person’s privacy and civil liberties. Dr. Alec Jeffrey, a former professor at the University of Leicester laboratory, consulted with his lawyers to develop the new type of technique called DNA profiling. His technique would prove that DNA fingerprinting (profiling) can individualize evidence compared to the blood typing. DNA profiling compares 13 standard STRs to form a profile. The analysis used by the scientists, uses PCR and STRs to profile an individual. It is highly unlike that two individuals’ identical numbers of repeats for all 13 STRs, will match, which DNA fails is hardly never due to a successful match of 385 million to 1. This makes DNA profiling the most accurate tool in Forensics.

DNA fingerprinting is a scientific technology involving the extraction, replication and arrangement of strands of an organism’s DNA. This results in the formation of a genetically distinctive fingerprint that is unique to the organism which the DNA sample was originally extracted from. Because of the specificity of a DNA fingerprint, the application of this technology can have a substantial influence on many aspects of society. Accessibility to a DNA database allows for higher efficiency in forensic investigations, personal identification, maternal and paternal testing. The availability of a national database to police officers and forensic scientists would equate to increased productivity in investigations and prosecution of suspects in a