Crime Scene: #2
Evidence being examined:
Forensic Science Used: Nucleic DNA
Question: Is the blood under Nathan Herron's nails James Newell's or John Hannah's?
Summary of the Science:
In investigations, evidence gathered from nucleic DNA is used whenever possible. DNA is an infallible indicator of identity. Each individual’s DNA is unique (an exception being the genetic code of twins), and cannot be altered to mislead investigators, unless the DNA of that individual is not actually given, and someone else’s is. When identifying the owner of a DNA sample, investigators use genetic fingerprinting, or DNA profiling. Two techniques for DNA profiling were developed simultaneously and independently by two groups: Kary Mullis, who invented PCR (Polymerase Chain Reaction), and Professor Sir Alec Jeffreys, who developed actual DNA fingerprinting. Years before, Jeffreys was allowed to conduct genetic research in a small laboratory owned by the University of Leicester. He and his part-time technician began noticing variations in the different genetic sequences of the samples they collected. In 1984, Jeffreys had what he describes as an ‘eureka’ moment. He realized what the pattern and unique characteristics in the genetic codes meant, that each person had a unique genetic fingerprint. A whole new field of science was discovered. A flood of cases came crashing in, one of the first being a paternity case. For almost 2 years, Jeffreys’ lab was the only one in the world using and studying genetic fingerprinting. Later, the use of genetic fingerprinting was expanded. In 1985, Jeffreys and his team created a variation of genetic fingerprinting called genetic profiling, specifically for forensic use that was faster and easier to use. Soon after, this variation was put to use. In the area, two girls had been raped and murdered, in separate crimes. A man had confessed to one of the crimes, and the police decided to employ genetic profiling to determine if he was responsible for the other crime as well. The result was that he was the criminal in neither of them, but the same person was responsible for both crimes. He had given a false confession. The police took DNA samples from males in the area, and eventually the perpetrator was found. The public began to trust the process more and more, and genetic profiling was used to put a serial murderer behind bars. A year after Jeffreys had discovered genetic fingerprinting in the UK, in 1985, Kary Mullis invented the PCR technique working at a biotechnology firm called Cetus Corporation. The first version of the PCR technique worked, but it was extremely labor-intensive and slow. Later that year, workers at Cetus, including Kary, created the first DNA Thermal Cycler, a device that rapidly heated and cooled the PCR tubes at varying temperatures and enabled the process to become a lot faster. Finally, there was a reliable and easy to identify people who had been at a crime scene, creating a new form of associative evidence.
DNA profiling entails studying the genetic sequence of an individual to determine their identity. Investigators take biological evidence from the crime scene and analyze it to determine the genetic sequence and thus the owner of the genetic material. Despite the fact that 99.9% of every person’s DNA sequence is exactly the same, studying that 0.1% provides enough information for the process to be successful. The process of genetic fingerprinting begins by extracting DNA from the nucleus of the cells comprising the biological evidence found at the crime scene. Biological evidence includes physical evidence such as bodily fluids that originated from a human, plant, or animal. Human DNA can be extracted from blood, hair roots, skin, semen, skeletal remains, or other bodily fluids. Locard’s Exchange Principle says that every person who enters or exits an area will deposit and/or remove physical material from the scene. Therefore, people are constantly leaving DNA everywhere, wherever we leave our cells. To extract DNA, cells must first be collected. The best way to do this is through a buccal swab, or a buccal smear, where you collect DNA from the inside of a person’s cheek. The steps afterward are simple: the cells have to be opened to release the DNA, the DNA must be purified and removed from all other biological substances that may contaminate it, and the DNA needs to be isolated. To open the cells, you take the buccal swab with the cheek cells, remove the tip of the swab, and place it into an Eppendorf tube. Lysis solution is added to the tube, then the tube is placed in warm water. The lysis solution has two ingredients called detergent and proteinase K that cause the cheek cells to open and release their DNA. Once the tube has been in the bath for long enough for the DNA to be released, the swab is removed from the tube and a concentrated salt solution is added that causes cellular debris to group together in one clump. The tube is placed in a centrifuge, which speeds up the process, causing cellular debris to clump at the bottom while strands of DNA are distributed throughout the top. A micropipette is used to separate the liquid at the top with the DNA in it from the debris at the bottom. The liquid is moved to a clean tube. Then, isopropyl alcohol is added to the solution and the tube is shaken then placed in a centrifuge again. The DNA will become clumped at the bottom of the tube, and when the liquid is removed and the DNA has dried, it is ready to be analyzed.
Although extracting DNA with this technique works, in some cases, the DNA samples provided are too small or damaged to be identified using the conventional methods of DNA fingerprinting. This is where PCR comes in. PCR is a technique that is used to create thousands to millions of copies of a piece of DNA, allowing forensic scientists to amplify one particular piece of DNA and make it easier to see and distinguish. PCR is just one technique employed in DNA profiling. It used to successfully identify DNA samples that are insufficient for conventional DNA profiling methods in some way. To conduct PCR, first DNA is extracted from a cell and placed in a special PCR tube. Then, 2 primers are added consecutively to the tube. They attach to each end of the segment of DNA that is being copied and ensure that that particular segment will be copied. Next, Nucleotides are added, genetic building blocks that together create the genetic code. DNA polymerase is as well, molecules that read the genetic code of the segment being copied and match nucleotides to create copies. The entire mixture is placed in a DNA Thermal Cycler that raises and lowers the temperature at specific times. It goes through different cycles alternating between 95 degrees, 50 degrees, and 72 degrees celsius. During each cycle, a double helix strand of DNA is taken and separated. Primers 1 and 2 then lock onto each single strand of DNA and prevent them from forming a double helix again. Then, the DNA polymerase is activated and starts to add the correct nucleotides to the single strands. Copies are created. The process is repeated 2 more times before copies of only the selected segment appear. Then it can be repeated over 30 times, where over a billion copies of the desired segment have been made. Once enough copies have been made, the DNA may finally be analyzed through DNA profiling.
A method of analyzing DNA and eventually profiling it is gel electrophoresis. In gel electrophoresis, the first step is to cut the DNA with restriction enzymes and load it onto agarose gel. The fragments of DNA on the gel are then subjected to an electric current, with a positive charge on one side and a negative charge on the other. Since all DNA is negatively charged, the DNA fragments will gradually move towards the positive charge. The fragments will become spread out throughout the gel, with the larger fragments closer to one side and the smaller fragments farther along, since the larger fragments will become stuck sooner. Afterwards, the fragments can be removed from the gel by a nylon membrane, or filter paper that is chemically treated to make the DNA single stranded, and then probed with radioactively labelled DNA that is complementary to the original DNA. As the radioactive DNA decays, it gives off light, which can be used to develop film and see the genetic sequence with the naked eye. A DNA banding pattern, or genetic fingerprint, is produced that can be analyzed and compared to other banding patterns, allowing scientists to identify the DNA and find unique features.
Genetic profiling over the years has become a lot simpler and quicker than it was when Jeffreys used it to help catch that serial killer. There are now national criminal databases in multiple countries containing genetic profiles of convicted criminals, making it easier to identify DNA by cross examining it with that of people who are so obviously predisposed to committing crime. When Jeffreys discovered genetic fingerprinting, he changed the entire field of genetics, leading to questions about how both our environment and our biological history are affected by our genes, and vice versa. And what are the implications of this? There are so many different ways genetics is affecting our lives today, and this was all made possible by the discovery that each individual possesses their own unique genetic code. Recently in genetics, scientists have discovered a gene called LGI2 that plays a vital role in epilepsy. Boule, the ‘sexy gene’, is now known to be responsible and required for sperm production in insects to mammals. Fusion genes, two otherwise normal and healthy genes that join together, are implicated in not only blood and marrow cancers but also a glandular cancer. In recent years, there have been countless other discoveries connecting certain genes or combinations of genes to different diseases and cancers. Now that scientists have greater knowledge of the causes, it will be easier to understand the different diseases/cancers and devise a cure. Today, scientists are attempting to formulate drugs that would ‘turn off’ and disable these genes, therefore rendering the disease or cancer powerless.
In the case of Crime Scene #2, blood was found underneath the fingernails of Nathan Herron, the victim. Since the amount of DNA was so small, PCR was needed to make copies of the existing DNA to process it. Afterwards, we went through the process of gel electrophoresis with our DNA. We poured the agarose gel, withdrew the plastic slide that made the wells, placed the DNA in the wells, then created a negative charge through the tray with a battery. Our two main suspects in this case were James Newell and John Hannah. After the murder, John Hannah was heard in prison confessing to a fellow prisoner that he and a friend killed Nathan Herron. He is known to have mental health issues. James Newell was the live-in boyfriend of Lori Herron, Nathan's mother, before the murder. His fingerprints were found at the crime scene. Unfortunately, after PCR and gel electrophoresis were conducted, we found that the DNA found under Nathon's fingerprints did not match either of the suspects'. Based on this evidence, we cannot conclude that James Newell or John Hannah murdered Nathan Herron.
Sources
http://en.wikipedia.org/wiki/DNA_profiling
http://www.csun.edu/~cmalone/pdf360/Ch16,17rDNA.pdf
http://www.exploreforensics.co.uk/dna-fingerprinting.html
http://www2.le.ac.uk/departments/emfpu/genetics/explained/profiling-history
http://learn.genetics.utah.edu/content/labs/pcr/
http://io9.com/5835215/10-recent-genetic-discoveries-and-the-diseases-they-will-help-treat
Evidence being examined:
Forensic Science Used: Nucleic DNA
Question: Is the blood under Nathan Herron's nails James Newell's or John Hannah's?
Summary of the Science:
In investigations, evidence gathered from nucleic DNA is used whenever possible. DNA is an infallible indicator of identity. Each individual’s DNA is unique (an exception being the genetic code of twins), and cannot be altered to mislead investigators, unless the DNA of that individual is not actually given, and someone else’s is. When identifying the owner of a DNA sample, investigators use genetic fingerprinting, or DNA profiling. Two techniques for DNA profiling were developed simultaneously and independently by two groups: Kary Mullis, who invented PCR (Polymerase Chain Reaction), and Professor Sir Alec Jeffreys, who developed actual DNA fingerprinting. Years before, Jeffreys was allowed to conduct genetic research in a small laboratory owned by the University of Leicester. He and his part-time technician began noticing variations in the different genetic sequences of the samples they collected. In 1984, Jeffreys had what he describes as an ‘eureka’ moment. He realized what the pattern and unique characteristics in the genetic codes meant, that each person had a unique genetic fingerprint. A whole new field of science was discovered. A flood of cases came crashing in, one of the first being a paternity case. For almost 2 years, Jeffreys’ lab was the only one in the world using and studying genetic fingerprinting. Later, the use of genetic fingerprinting was expanded. In 1985, Jeffreys and his team created a variation of genetic fingerprinting called genetic profiling, specifically for forensic use that was faster and easier to use. Soon after, this variation was put to use. In the area, two girls had been raped and murdered, in separate crimes. A man had confessed to one of the crimes, and the police decided to employ genetic profiling to determine if he was responsible for the other crime as well. The result was that he was the criminal in neither of them, but the same person was responsible for both crimes. He had given a false confession. The police took DNA samples from males in the area, and eventually the perpetrator was found. The public began to trust the process more and more, and genetic profiling was used to put a serial murderer behind bars. A year after Jeffreys had discovered genetic fingerprinting in the UK, in 1985, Kary Mullis invented the PCR technique working at a biotechnology firm called Cetus Corporation. The first version of the PCR technique worked, but it was extremely labor-intensive and slow. Later that year, workers at Cetus, including Kary, created the first DNA Thermal Cycler, a device that rapidly heated and cooled the PCR tubes at varying temperatures and enabled the process to become a lot faster. Finally, there was a reliable and easy to identify people who had been at a crime scene, creating a new form of associative evidence.
DNA profiling entails studying the genetic sequence of an individual to determine their identity. Investigators take biological evidence from the crime scene and analyze it to determine the genetic sequence and thus the owner of the genetic material. Despite the fact that 99.9% of every person’s DNA sequence is exactly the same, studying that 0.1% provides enough information for the process to be successful. The process of genetic fingerprinting begins by extracting DNA from the nucleus of the cells comprising the biological evidence found at the crime scene. Biological evidence includes physical evidence such as bodily fluids that originated from a human, plant, or animal. Human DNA can be extracted from blood, hair roots, skin, semen, skeletal remains, or other bodily fluids. Locard’s Exchange Principle says that every person who enters or exits an area will deposit and/or remove physical material from the scene. Therefore, people are constantly leaving DNA everywhere, wherever we leave our cells. To extract DNA, cells must first be collected. The best way to do this is through a buccal swab, or a buccal smear, where you collect DNA from the inside of a person’s cheek. The steps afterward are simple: the cells have to be opened to release the DNA, the DNA must be purified and removed from all other biological substances that may contaminate it, and the DNA needs to be isolated. To open the cells, you take the buccal swab with the cheek cells, remove the tip of the swab, and place it into an Eppendorf tube. Lysis solution is added to the tube, then the tube is placed in warm water. The lysis solution has two ingredients called detergent and proteinase K that cause the cheek cells to open and release their DNA. Once the tube has been in the bath for long enough for the DNA to be released, the swab is removed from the tube and a concentrated salt solution is added that causes cellular debris to group together in one clump. The tube is placed in a centrifuge, which speeds up the process, causing cellular debris to clump at the bottom while strands of DNA are distributed throughout the top. A micropipette is used to separate the liquid at the top with the DNA in it from the debris at the bottom. The liquid is moved to a clean tube. Then, isopropyl alcohol is added to the solution and the tube is shaken then placed in a centrifuge again. The DNA will become clumped at the bottom of the tube, and when the liquid is removed and the DNA has dried, it is ready to be analyzed.
Although extracting DNA with this technique works, in some cases, the DNA samples provided are too small or damaged to be identified using the conventional methods of DNA fingerprinting. This is where PCR comes in. PCR is a technique that is used to create thousands to millions of copies of a piece of DNA, allowing forensic scientists to amplify one particular piece of DNA and make it easier to see and distinguish. PCR is just one technique employed in DNA profiling. It used to successfully identify DNA samples that are insufficient for conventional DNA profiling methods in some way. To conduct PCR, first DNA is extracted from a cell and placed in a special PCR tube. Then, 2 primers are added consecutively to the tube. They attach to each end of the segment of DNA that is being copied and ensure that that particular segment will be copied. Next, Nucleotides are added, genetic building blocks that together create the genetic code. DNA polymerase is as well, molecules that read the genetic code of the segment being copied and match nucleotides to create copies. The entire mixture is placed in a DNA Thermal Cycler that raises and lowers the temperature at specific times. It goes through different cycles alternating between 95 degrees, 50 degrees, and 72 degrees celsius. During each cycle, a double helix strand of DNA is taken and separated. Primers 1 and 2 then lock onto each single strand of DNA and prevent them from forming a double helix again. Then, the DNA polymerase is activated and starts to add the correct nucleotides to the single strands. Copies are created. The process is repeated 2 more times before copies of only the selected segment appear. Then it can be repeated over 30 times, where over a billion copies of the desired segment have been made. Once enough copies have been made, the DNA may finally be analyzed through DNA profiling.
A method of analyzing DNA and eventually profiling it is gel electrophoresis. In gel electrophoresis, the first step is to cut the DNA with restriction enzymes and load it onto agarose gel. The fragments of DNA on the gel are then subjected to an electric current, with a positive charge on one side and a negative charge on the other. Since all DNA is negatively charged, the DNA fragments will gradually move towards the positive charge. The fragments will become spread out throughout the gel, with the larger fragments closer to one side and the smaller fragments farther along, since the larger fragments will become stuck sooner. Afterwards, the fragments can be removed from the gel by a nylon membrane, or filter paper that is chemically treated to make the DNA single stranded, and then probed with radioactively labelled DNA that is complementary to the original DNA. As the radioactive DNA decays, it gives off light, which can be used to develop film and see the genetic sequence with the naked eye. A DNA banding pattern, or genetic fingerprint, is produced that can be analyzed and compared to other banding patterns, allowing scientists to identify the DNA and find unique features.
Genetic profiling over the years has become a lot simpler and quicker than it was when Jeffreys used it to help catch that serial killer. There are now national criminal databases in multiple countries containing genetic profiles of convicted criminals, making it easier to identify DNA by cross examining it with that of people who are so obviously predisposed to committing crime. When Jeffreys discovered genetic fingerprinting, he changed the entire field of genetics, leading to questions about how both our environment and our biological history are affected by our genes, and vice versa. And what are the implications of this? There are so many different ways genetics is affecting our lives today, and this was all made possible by the discovery that each individual possesses their own unique genetic code. Recently in genetics, scientists have discovered a gene called LGI2 that plays a vital role in epilepsy. Boule, the ‘sexy gene’, is now known to be responsible and required for sperm production in insects to mammals. Fusion genes, two otherwise normal and healthy genes that join together, are implicated in not only blood and marrow cancers but also a glandular cancer. In recent years, there have been countless other discoveries connecting certain genes or combinations of genes to different diseases and cancers. Now that scientists have greater knowledge of the causes, it will be easier to understand the different diseases/cancers and devise a cure. Today, scientists are attempting to formulate drugs that would ‘turn off’ and disable these genes, therefore rendering the disease or cancer powerless.
In the case of Crime Scene #2, blood was found underneath the fingernails of Nathan Herron, the victim. Since the amount of DNA was so small, PCR was needed to make copies of the existing DNA to process it. Afterwards, we went through the process of gel electrophoresis with our DNA. We poured the agarose gel, withdrew the plastic slide that made the wells, placed the DNA in the wells, then created a negative charge through the tray with a battery. Our two main suspects in this case were James Newell and John Hannah. After the murder, John Hannah was heard in prison confessing to a fellow prisoner that he and a friend killed Nathan Herron. He is known to have mental health issues. James Newell was the live-in boyfriend of Lori Herron, Nathan's mother, before the murder. His fingerprints were found at the crime scene. Unfortunately, after PCR and gel electrophoresis were conducted, we found that the DNA found under Nathon's fingerprints did not match either of the suspects'. Based on this evidence, we cannot conclude that James Newell or John Hannah murdered Nathan Herron.
Sources
http://en.wikipedia.org/wiki/DNA_profiling
http://www.csun.edu/~cmalone/pdf360/Ch16,17rDNA.pdf
http://www.exploreforensics.co.uk/dna-fingerprinting.html
http://www2.le.ac.uk/departments/emfpu/genetics/explained/profiling-history
http://learn.genetics.utah.edu/content/labs/pcr/
http://io9.com/5835215/10-recent-genetic-discoveries-and-the-diseases-they-will-help-treat