Deoxyribonucleic Acid in Forensics

Christopher Beau_James Smith?

Criminal Justice, South College?

CMJ4101 – Forensic Science?

Dr. Tharinia Oyegun?

December 12, 2023?

Deoxyribonucleic Acid in Forensics???

Introduction?

Deoxyribonucleic Acid is more commonly known as DNA. While many people understand that DNA is used to solve crimes, few know exactly how it occurs. Although there are many techniques utilized in the crime-solving process, it has been found that the use of DNA provides a more accurate and definite answer. This paper will discuss what DNA actually is, how and when it began to be used in forensic sciences, and how it is being utilized to solve crimes in the world today.??

Deoxyribonucleic Acid??

Deoxyribonucleic Acid, DNA, is the molecule that carries an individual’s genetic information for the functioning, growth, reproduction, and development of an organism. Two polynucleotide chains coil around one another to form a double helix which creates a polymer known as DNA. Each human around the globe contains a DNA that is unique only to a single individual. DNA is inherited from one’s parents and is contained in nearly every cell of the human body.?

Each double-stranded DNA molecule consists of forty-six chromosomes. Which are divided into twenty-three chromosome pairs. The sequence of the DNA is similar to a blueprint for development. Within the DNA sequence are determined mental capacities that are essential to human life. This sequence is also known to contain mutations or variations that may cause susceptibility to diseases. Each sequence that provides instructions to produce protein is referred to as a gene. Most people understand that no two people carry the same set of genes, and this is due to DNA. There are even some identical twins that do not have the same DNA.??

How and When DNA Began to be Used in Forensics?

DNA was discovered in the late 1860s by Friedrich Miescher, a Swiss chemist. In 1953, Biologist James Watson and Physicist Francis Crick found that DNA exists as a three-dimensional double helix. This accelerated DNA research and its applications. In the early 1980s, DNA was being used to establish paternity in some cases, but it was utilized to solve the first of many crimes in 1986. A young geneticist, Alec Jeffreys, assisted the police in solving a murder case using DNA that was found at the crime scene. Before this, scientists utilized serological testing when genetic testing was a must, according to the DNA Diagnostics Center (n.d.). Serological testing, comparing the Human Leukocyte Antigen (HLA) found in the cells of the body, was only estimated to be 80% accurate.?

It took much more than solving one murder case with the use of DNA to convince people that this was a safe, unbiased, accurate way to determine guilt. It took many years of legal brainstorming to decide when and how courts would allow DNA evidence in cases. Uniform standards had to be created for laboratories and databases. A decision had to be made on how the courts could, ethically, keep a database of felons’ DNA. A set of uniform testing procedures had to be built, as well. Once these things were put into place, several wrongfully convicted people were freed.?

How DNA is Utilized to Solve Crimes in the World Today?

The process of using DNA to solve crimes has come a long way in the last few decades. It has been mentioned that DNA fingerprinting was first used in 1986 to exonerate a man by the name of Richard Buckland on the charges of rape and murder. However, DNA testing now involves much more than fingerprinting. Modern DNA testing is more in-depth with the use of bodily fluids and tissue. This allows results to be much more accurate, specific, and reliable.??

Although all people carry human DNA, there are regions of variation within the DNA that make each person’s DNA unique. Some people have noncoding regions that contain repeating units of DNA that vary in length. According to Karen Norrgard, Ph.D., scientists have discovered a certain type of repeat known as a short tandem repeat (STR) that differs by ethnicity (2008). Interpol has found 10 core STR loci for the United Kingdom and Europe, 9 STR loci have been revealed for Indian populations, and the Federal Bureau of Investigation (FBI) has identified 13 STR loci for the United States.??

In the United States, utilizing the 13-STR profile is a common means of identification. It is used in identifying human remains, may exclude or establish paternity of a child, or to match a suspect to a sample retrieved from a crime scene. There is considerable statistical strength behind the 13-STR profile process. Going by the FBI 13-STR allele frequencies, the chances of two unrelated Caucasians with identical STR profiles are estimated to be 1 in 575 trillion (Norrgard, 2008). This means that it is almost impossible to reveal a false positive match with DNA.??

In forensic DNA analysis, DNA is extracted from a sample. According to the Bureau of Criminal Apprehension, this is the first step of a four-step process for DNA analysis (n.d.). This sample does not need to be a significant amount. One nanogram of DNA is enough to provide good data for analysis. After extracting the DNA, scientists measure and assess the quantity and quality of the DNA to ensure that it is human rather than animal or bacterial. This is referred to as the quantitation step. After testing positive as human DNA, the area of DNA that contains STR is then polymerase chain reaction amplified and resolved, providing a 13-STR profile. This amplification step ensures the quantity and quality of the DNA sample is sufficient. Because of the need to differentiate single-base differences, polymerase chain reaction products are typically resolved using automated DNA sequencing technologies with software that recognizes allele patterns by comparison to a known "ladder." This process of categorizing DNA molecules is known as the capillary electrophoresis step. Analysts then perform the exact procedure with a sample from a suspect, for example. The 13-STR profile of the suspect will be compared to the 13-STR profile discovered in the first sample. If the two samples are identical, a match has been discovered.??

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?References?

Bureau of Criminal Apprehension. (n.d.). DNA Testing Procedures. https://dps.mn.gov/divisions/bca/bca-divisions/forensic-science/Pages/dna-procedures.aspx??

DNA Diagnostics Center. (n.d.). Introduction to DNA Testing History. https://dnacenter.com/history-of-dna-testing/???

Norrgard, Karen, Ph.D. (2008). Forensics, DNA Fingerprinting, and CODIS. https://nature.com/scitable/topicpage/forensics-dna-fingerprinting-and-codis-736/#:~:text=DNA%20Extraction%20and%20Analysis,of%20STR%20sizes%20(alleles).???