Introduction
DNA (deoxyribonucleic acid) is the hereditary information in man and nearly all other organisms. All the body cells in a human being contain the same DNA material with especially high concentration of this hereditary material occurring within the cell nucleus (nuclear DNA). However some traces of the hereditary information can also be found within the mitochondria part of a cell. This type of DNA material is referred to as mitochondrial DNA (mtDNA) (“What is DNA?” 2018). The genetic information contained within the DNA is stored in the form of codes, each comprising of four chemical bases: adenine (A), cytosine (C), guanine (G), and thymine (T). Studies have revealed the human DNA is made up of an estimated three billion chemical bases (adenine, cytosine, guanine and thymine), and nearly 99% of these chemical bases are identical across the human population (“What is DNA?” 2018). The order, or arrangement of the chemical bases within the codes is pivotal in the determination of the genetic information presented for maintaining and building an organism. It is also imperative to note that the chemical bases making up the body DNA pair up, with adenine pairing with thymine, and cytosine pairing with guanine to create units known as base pairs. Additionally, the chemical bases are also appended to a phosphate and a sugar molecule to form a nucleotide (base + phosphate molecule + sugar molecule) (“What is DNA?” 2018). Furthermore, nucleotides are arrayed in two long strands that occasionally intertwine to form a double helix spiral. DNA can replicate and individual strands of DNA within the double helix spiral can function as a pattern for the duplication of the base sequences. This characteristic of the DNA molecule is crucial during cell division. Each daughter cell should possess the exact DNA copy as the in the parent cell (“What is DNA?” 2018).
Who came up with DNA?
In April, 1953, English physicist and American biologist Francis Crick and James Watson publicized that they had discovered what was then termed as “the secret of life” (the double helix strand that constitutes the DNA). The duo described DNA as the molecule encompassing the hereditary information in living organisms (Borowski, 2018). Even though Watson and Crick have been credited with the discovery of DNA, their studies and findings were founded on the 1869 works of Johannes Friedrich Miescher, a Swiss chemist who first developed an understanding of DNA. Friedrich had set out to study the protein content in white blood cells when he figured out a substance within the nuclei of white blood cells that possessed dissimilar chemical properties as that of proteins. He named this component of white blood cells nuclei “nuclein” (“The discovery of DNA,” 2018).
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What necessitated the use of DNA in Forensic Analysis?
One of the leading causes of the initiation of DNA analysis into forensic analysis was little dependability on witness accounts. Witness accounts for a number of reasons, proved unreliable. First, there was the question of accuracy of eyewitness testimonies. Several studies exposed that the human memory could be easily influenced via third party introduction of false facts. One particular study revealed that witnesses false remember seeing images that did not exist during particular incidences when false information is instituted into an individual’s reminiscence by a third party (Lombardo, 2018).
In addition, it was also established that investigations should no longer solely depend on eyewitness testimonies since they wholly relied on only peoples’ ability to remember. There was therefore the need to come up with a more accurate approach to forensic analysis. Additionally, the human memory was also established to possess the vulnerability to be partial. This is especially so when trigger statements are used by a third party, causing clouding of the judgment of the witness, and also confusing the witnesses’ memory and making it hard to remember the events exactly as they unfolded (Lombardo, 2018). Furthermore, criminal investigations have always entailed retelling of accounts of criminal occurrences. Reciting these accounts in the same is always difficult, and by failing to retell the stories in a neutral fashion every time one is called upon, it was revealed that memory suffers in the process. For example, narrating criminal accounts while trying to tailor them to the listeners was found to be detrimental to the human memory (Lombardo, 2018).
There was also a need to come up with a more precise strategy to forensic analysis since eyewitness accounts were found to be capable of condemning the wrong persons. Use of leading questions for example during criminal investigations were uncovered to be capable of causing victims and witnesses alike to “remember” occurrences that did not even exist. Summed up with the great value and emphasis that juries placed on witness accounts, such false memories were established as one of the culprits behind wrongful detention (Lombardo, 2018).
Finally, Lombardo (2018) also revealed that one of the reasons that necessitated the deployment of DNA in forensic analysis was because eyewitness accounts could be fabricated by the witnesses as a result of fear, or nervousness. The immense pressure that eyewitnesses are faced with in the courtroom for example was found to be able to influence an individual’s memory. The pressure resulting from being counted on for a case to be solved was found to be capable of causing witnesses to cite accounts that are inaccurate or even entirely wrong. In addition, emotions were also ascertained to lead witnesses to remembering events differently. When witnesses get emotional, their ability to precisely recall the order of happenings or even critical niceties that could be fundamental in solving a case is affected (Lombardo, 2018). Use of DNA information in forensic analysis was found to be almost 100% reliable since it offered biological evidence in criminal cases as far as certain risks such as contamination of the material containing the DNA were eliminated (Juengst, 2014).
How was DNA extracted?
The process of DNA isolation from cells has undergone a lot of evolution. The first method of DNA extraction from cells was simpler in technique and execution compared to the present day criteria. The first routine laboratory criteria for DNA isolation was developed by Stah and Meselson in 1958 (Mirmomeni, Majd, Sisakhtnezhad & Doranegard, 2010). The duo recruited a salt density gradient centrifugation protocol to extract DNA from bacterial samples of Escherichia coli. This method was aimed at achieving effectual disruption of the DNA containing cells, denaturing of nucleoprotein complexes, inactivation of nucleases and other related enzymes, isolation of chemical and biological contaminants, and lastly, DNA precipitation (Mirmomeni, Majd, Sisakhtnezhad & Doranegard, 2010). Below is a summary of the procedure for the salting-out DNA extraction method.
The first step in this process is cell disruption and digestion using SDS-proteinase K.
This is followed by adding highly concentrated salts, usually 6 molar sodium chloride.
Centrifugation of the mixture is the next stage. It allows proteins to settle at the bottom of the centrifuge tube whereas the DNA containing section floats above the protein layer.
The DNA containing section is then relocated to a fresh vial. Here, the DNA is precipitated using isopropanol or ethanol (Mirmomeni, Majd, Sisakhtnezhad & Doranegard, 2010).
Another method for DNA extraction was the phenol-chloroform DNA extraction technique. Below is a summary of the procedures involved in this technique (Selamn-Ayetey, 2007).
Following the inactivation of proteinase K, 0.5 ml of saturated phenol (pH 8) is added to the micro tubes containing the inactivated proteinase K. This is then followed by gently shaking the tubes by hand for about 5 minutes.
The micro tubes are then to be centrifuged at 8000 revolutions per minute for five minutes.
The supernatant is then transferred into another tube where it is mixed with 220 μL of phenol and 220 μL of chloroform.
The mixture is then centrifuged again at 8000 revolutions per minute for another five minutes to achieve an aqueous phase.
The next step involves the addition of 440 μL of chloroform to the aqueous phase, followed by centrifugation yet again at 8000 rpm for an additional five minutes.
The supernatant after centrifugation is then transferred into a new tube whereby 3 M, pH 5.2 sodium acetate and 100% ethanol (both thrice as much as the volume of the supernatant) are added.
The setup is then left to stay overnight for DNA precipitation at a constant temperature of -20°C or for 60 minutes at a temperature of -80°C.
The precipitated DNA is then collected through centrifugation over a 30 minute duration at a stable temperature of 4°C.
It is then followed by washing with 70% ethanol, after which it is air dried at room temperature.
The final step involves re-suspension of the DNA material in 30-50 μL of TE buffer or double distilled water.
What machine reads DNA?
DNA information is not of much importance to forensic analysis until after it has been interpreted. Establishment of the DNA sequence (pattern) in a given source of hereditary material is the most crucial stage to solving forensic investigations. A DNA sequencer is the machine used to automate the process of DNA sequencing. This machine was however invented several years later after the publication of the invention of DNA. The DNA sequencer was the creation of Lloyd M. Smith in the year 1987 (Lehrach, 2013). This tool is used to evaluate the order in which the four chemical bases (adenine, cytosine, guanine, and thymine) occur within the DNA strands. This sequence is then reported by the machine in the form of a text string referred to as a read. Recently, optical instruments have found their way into the field of DNA research. These instruments are used to dissect light signals from fluorochromes. Fluorochromes are appended to the nucleotides (Lehrach, 2013).
What type of materials are used to obtain DNA?
DNA material can be acquire from various body parts and body fluids. First, the human blood is an important source of human DNA. However, DNA information is only present within the white blood cells and not red blood cells. The latter do lack cell nuclei where hereditary information is always encoded (Lerner & Lerner, 2012). The human saliva also contains cellular substances from which DNA can be extracted. Therefore, DNA can be extracted from cigarette butts, bite marks, and even postage stamps on envelopes. Human urine can also be used to source human DNA. It is however important to note that urine in itself does not contain any DNA information. However, urine may have epithelial cells which always contain DNA (Lerner & Lerner, 2012). DNA can also be obtained from the hair follicles. Hair follicles contain cellular material that has been established to be rich in DNA. In addition, sperm heads, epithelial cells, bones, teeth, and any other body tissue as long as they have not undergone decomposition are imperative sources of DNA (Lerner & Lerner, 2012).
Who initiated DNA profiling and how did he know that this forensic analysis method would be successful?
British geneticist, Sir. Alec Jeffreys, developed DNA profiling in 1984. He had been working at the University of Leicester, Genetics Department. He would later partner with Dave Werrett and Peter Gill (both from the Forensic Science Service) to complete his studies in DNA profiling (Jeffreys, 2013). Upon completion, DNA profiling was then used forensically for the first time in cracking the murder litigations in which two teenagers, Dawn Ashworth, and Lynda Mann had been raped and subsequently killed in Narborough, Leicestershire in 1986 and 1983 respectively (Jeffreys, 2013). Sir. Alec Jeffreys knew that DNA fingerprinting would be a success in forensic analysis since just like fingerprints, DNA characteristics are unique to an individual across the human population. DNA could also be used to crack cases where there were suspects but no witnesses. The genetic material collected from the crime scene could be tested and then compared with those of the suspects of a criminal offense (Jeffreys, 2013).
How and when did the use of DNA become a big turning point in the forensics field?
How did DNA fingerprinting become popular?
DNA fingerprinting gained popularity following its usage to solve two separate cases involving two teenagers who had been raped then murdered. In 1983, the quiet and little village of Narborough, Leicestershire was put on the forensic map following two successive acts of cold-heartedness. 15 year old Lynda Mann had been found raped and killed, and exactly three days later, another 15 year old, Dawn Ashworth was also found raped and murdered not too far away from the University of Leicester (Hill, 2016). With the use of Restriction Fragment Length Polymorphism (RFLP) based DNA technology, Sir. Jeffreys was called upon to study and compare semen samples from the two rape and murder victims and blood samples drawn from the key murder suspect in the two cases, 17 year old Richard Buckland. Buckland had been police custody for almost three years. Dr. Jeffreys’ tests revealed that the DNA in the semen samples did not match Buckland’s DNA, and as a result, Richard was freed (Hill, 2016). Dr. Jeffreys’ study also publicized that the same suspect was responsible for both crimes. With the identity of the DNA sequence of the killer known, police investigations were fastened within the City of Leicester to apprehend the murderer. Several men from various towns within Leicestershire had their blood tested for the suspect’s blood type (Lerner & Lerner, 2012). The blood type of the killer had been revealed to be type A and containing enzyme PGM + 1. 27 year old Colin Pitchfork was subsequently arrested for both the rape and murder of Lynda Mann and Dawn Ashworth in the year 1987. His DNA and the DNA present in the semen were found to be perfect matches. In the same year, Pitchfork became the first human to be successfully identified, arrested and prosecuted, thanks to DNA fingerprinting. Pitchfork was sentenced to life with a minimum jail term of 30 years (Lerner & Lerner, 2012).
Further breakthroughs in the forensic field were attained when DNA once proved vital in solving of several other case such as robbery and paternity disputes. In the case of robbery cases, DNA samples collected at the crime scene were compared against the DNA of suspects. On its side, paternity disputes were solved by DNA fingerprinting by comparing the DNA of the baby and that of the supposed father. The father was then declared to have either sired the baby or not, depending on the similarities of their DNA sequences (Lerner & Lerner, 2012).
DNA profiling has continued to advance ever since it was publicized during mid-20 th century. Today, a sweaty palm or even an indiscernible dusting of dandruff is enough to classify criminal offenders. In addition, it is possible today to pick DNA profiles from single cells with an accuracy level of one billion to one. This technology has allowed detectives to collect DNA identities from materials such as door surfaces, walls, and even from pieces of plastic (Fickling, 2002). It nearly impossible today to commit a crime without leaving behind any traces. Fickling said, “You'd have to wear a space suit to stop yourself from leaving traces. You can identify cells on the paper, so you can work out where it's come from and who's touched it.” Progressions in the forensics field have even been able to identify the thrower of a punch. This has been made possible by studying the cells left behind on the skin surface of the victim. This cannot be prevented even by wearing latex gloves since some tiny cells are still capable of passing through the gloves and been deposited on the skin of the victim (Fickling, 2002). DNA fingerprinting has made forensic analysis simpler to accomplish. Many victims of criminal activities have also been able to find justice, thanks to advancements in DNA profiling.
Conclusion
DNA profiling has gone through tremendous technological advancements since its initiation in the 1950s. The progressions in DNA fingerprinting have the same magnitude of effects on the field of forensic analysis. From the identification and detention of the first man using this technology in the year 1987, DNA fingerprinting has continuously proved its significance in unravelling several criminal occurrences where witness accounts alone would have not been enough. Some of the criminal activities even lacked witness accounts but were still amicably solved, thanks to DNA profiling. DNA profiling has also proven its worth in non-criminal sectors such as disputed parentage. In addition, DNA fingerprinting is also pivotal in the diagnosis of genetic illnesses, cloning, and manufacture of vaccines. DNA fingerprinting is also relevant to agriculture. This technology has been recruited to boost agricultural productivity by designing of genetically modified organs.
References
Borowski, S. (2018). The other discoveries of DNA. Retrieved from https://www.aaas.org/other-discoverers-dna
Fickling, D. (2002). Breakthrough in DNA fingerprinting. Retrieved from https://www.theguardian.com/science/2002/oct/29/genetics.science
Jeffreys, A.J. (2013). The man behind the DNA fingerprints: an interview with Professor Sir Alec Jeffreys. Investigative Genetics, 4 (21). Doi: 10.1186/2041-2223-4-21
Juengst, E.T. (2014). Human genome project. In B. Jennings (Ed.), Bioethics (4 th ed., vol. 2). Farmington Hills, Michigan: Macmillan Reference USA.
Lehrach, H. (2013). DNA sequencing methods in human genetics and disease research. PubMed Central, 5 (34). Doi: 10.12703/P5-34
Lerner, B.W., & Lerner, K.L. (2016). Worldmark Global Health and Medicine Issues. Boston: Cengage.
Lombardo, C.R. (2018). 8 predominant pros and cons of eyewitness testimony. Retrieved from https://connectusfund.org/8-predominant-pros-and-cons-of-eyewitness-testimony
Melissa, S.H. (2016). Biology. Farmington Hills, Michigan: Macmillan Reference USA.
The discovery of DNA. (2018). Retrieved November 25, 2018 from https://www.yourgenome.org/stories/the-discovery-of-dna
What is DNA? . (2018). Retrieved from https://ghr.nlm.nih.gov/primer/basics/dna
