DNA as an Indispensable Forensic Science Tool - Assignment Example

DNA as an Indispensable Forensic Science Tool Definition of DNA DNA is a fantastic device now available to the criminal justice system where acquitted people can substantiate their claims. Each has a unique portion of the DNA structure. It is a fundamental unit of heredity. Each gene with DNA specification is designed to carry out various tasks of controlling the genetic traits of our cells. The genetic factor is a vast molecule made by linking series of repeating units termed as nucleotides. Nucleotide has sugar phosphorus and a nitrogen called base. Bases with the DNA structure are adenine (A), guanine (G), cytosine (C) and thymine (T). Bases on each strand align in a double-helix configuration known as base pairing. Order of the bases distinguishes different DNA strands (Richard, 2007). When doing the DNA testing it is then taken from two sources the cell’s nucleus and the cell’s mitochondria. Definition for forensic science The use of scientific principles to the art of criminal investigation is forensic science. It is a valuable tool in which juror’s tend to rely therefore it calls for accuracy and reliability in order to help prevent wrongful convictions. Some of the crime scene investigations that have been done by the forensics are the hair analysis. Work of DNA DNA is the genetic code for producing proteins made by combining amino acids. Each group of three nucleotides e.g. G-A-G codes for the amino acid called glutamine while C-G-T codes for alanine. Protein is not likely to function well if a nucleotide changes and becomes the basis for diseases and health issues. The proteins produced have roles such as enzymes are meant to speed up the chemical reaction. Cell transport protein is responsible in the association in the movement of materials in the cell. Replication of DNA It is a process in which the DNA copies. It happens before production of gametes or reproductive cells. Replication of the DNA begins with the unwinding of the DNA strand of the double helix. Once each strand is exposed to free collection of nucleotides it will be used to recreate the double helix by base pairing. Polymerase enzymes are responsible for unwinding, keeping and assembling new strands of DNA. The technique used for replicating small quantities of broken pieces of DNA in a crime scene outside a living cell is Polymerase chain reaction. Forensic scientists have been able to make billions of copies of DNA strands in the laboratory as a process of mimicking the DNA replication. DNA fingerprint DNA fingerprint uses the process of gel electrophoresis where the jelly-like substance is used to separate DNA into different sized particles. It creates patterns termed as fingerprints. There are steps followed when conducting fingerprinting i.e. removal. When doing extraction the cells are isolated and treated with chemicals to release chromosomes from the nucleus. Next step is that restriction enzymes recognize and cut at different sequences. It then leads to the separation of the DNA fragments by electrophoresis where DNA charged and attracted to a positive end. Shorter fragments will travel farther. The DNA stains are used to show the branding patterns. Use of DNA fingerprinting is effective in that it can match crime scene DNA with a suspect. Forensic scientists can identify the human remains and free a falsely imprisoned individual. DNA typing Tandem repeat is a term used to describe the portions of the DNA molecule that contain sequences of bases that are recurrent. The tandem repeats are important to a forensic scientist because it offers a means of differentiating one individual from the other using data typing. It acts as fillers between the coding regions of the DNA. First basis of DNA typing is restriction fragment length polymorphism which associates with long repeating strands of DNA (John, 2008). Blotting process involves the transfer of fragments to a nylon membrane using southern. After hybridization, the plastic sheet is placed against a ray of films and exposed for four days. Typical DNA fragment pattern of two brands will be pop. Polymerase chain reaction testing Polymerase chain reaction testing offers a distinct benefit to the forensic scientist for it can magnify minute quantities of DNA. First process is to heat strands to separate it; primers are additives that hybridize with the strands. DNA polymerase and free nucleotides are added to rebuild each of the separated strands. The gene strands that are no longer than a hundred bases are best used in PCR (McGraw, 2011). Advantages of polymerase chain reaction testing Using shorter genetic strands is expected to be more stable and less subject to degradation caused by adverse environmental conditions. It can also amplify minute sizes of DNA hence overcoming the limited sample size problem often associated with crime scene evidences. When comparing it to the long RFLP which usually break apart under the adverse not uncommon during crime scene it is viewed to be more accurate. Restriction fragment length polymorphism Use of restriction enzymes cuts defined length of the DNA. The term polymorphism is an inherited differences found among the individuals. RFLP is specific to a single clone enzyme arrangement. The probe hybridizes with one or more fragments of the digested DNA sample. Although DNA fingerprinting and RFLP is useful, it is no more the preferred method for DNA profiling. Reason is that must an entire DNA sample; it is hard to copy a full DNA sample to PCR, and now STR analysis is the most preferred. Short tandem repeats analysis According to Christine and Kean (2012) short tandem, repeats analysis has emerged as the most successful and widely used DNA profiling procedure. STR’s are locations on the chromosome with short courses that keep repeating themselves within the DNA molecule. They are very useful signs for identification; reason is that they are in great quantity throughout the human genome. The advantages of STR are that it consists of repeating sequences of the base length, and the entire strand is short. Another importance is it is less vulnerable to deprivation and may often recover from bodies and stains that have been exposed to decomposition. Because of its short strands it is ideal for PCR multiplication thus avoiding sample size limited problem during the crime scene. STR process is quite attractive to forensic scientists because a hundred of its types are in the human genes. Characterizing more STR’s the smaller the percentage of the population from which a particular combination of STR can originate. Multiplexing with the help of the PCR technology can help one extract and amplify blend of different STR. Standardizing short tandem repeat testing According to Stuart & Jon, (2014) U.S crime laboratories have standardized on 13 STR’s for entry into a national database. Individualization can be obtained by analyzing, multiplexing and determining the product of their frequencies. The procedure that can spot more than one DNA marker in a single analysis is multiplexing. Another tool available for the DNA analyst is to type STRs located on the Y chromosome specifically for male. Y-STRs will be useful when multiple males involves in sexual assaults. Analysis of the Y STR will have one band unlike the conventional STR which derives from two chromosomes and has two bands. Therefore, it is less complicated in interpretation and appearance. Mitochondrial DNA It is another type of DNA used for individual characterization. Mitochondrial DNA is outside the cell’s nucleus and inherited from the mother. Provision of energy that our bodies use for functioning is from mitochondria. Several loops of mitochondria are in single mitochondria. Mitochondrial DNA typing is best reserved for samples such as hair. Forensic analysis of mDNA is time-consuming, demanding and pricey when compared to nuclear DNA analysis. Sequencing is used to determine the order of base pairs of the two regions of mDNA. Combined DNA index system DNA typing is the ability to compare DNA types recovered from crime scene evidence to those of convicted criminals and sex offenders. It is a computer software program developed by the FBI. The software is meant to maintain local, state and national databases of DNA profiles from convicted offenders, profiles of missing persons and unresolved crime scenes. The databases are not only used to make direct matches but also conduct familial searching. DNA database has allowed a quick comprehension of the suspects through comparing new crime sample and that existing in the database. There are many advantages with this technique in that there is a potential benefit of identifying bodies provided they find individuals profile. Despite the many advantages of this technique, controversies arose in that whether keeping DNA samples for the victims who are honest. There also been complaints of righteous people found matches to DNA of those in the crime scene without their involvement. Blotting techniques Probes are used to detect specific molecules, but then because probes cannot be directly applied to the gel blotting techniques were initially utilized. There are various types of blotting techniques. Southern blot is in DNA analysis where it is extracted, separated with electrophoresis and then transmitted to the membrane. In order to identify and to hybridize to specific sequences, there is a need to add labeled probes. Western blot is for protein detection; the SDS-PAGE is used to separate the proteins for it to be transferred to the membrane. Visualizing the band is done by specific antibodies followed by a substrate. Northern blot aids in the study gene expression just like western blot except that the gene analyzed is the RNA. Eastern blot is used to study proteins considered to be an extension of the western blot. The southwestern blot combines the features of the south and western blot. It is for the rapid characterization of DNA binding proteins and their sites. Low copy number DNA analysis A technique developed by forensic science service is to help increase the sensitivity of DNA profiling methods. Issues like small amount of samples of degraded DNA often lead to completely negative results. The increased number of PCR cycles with standard techniques. Forensic DNA phenotyping improves sensitivity. Identification of phenotypic characteristic such as skin color, hair color and eye color in a study known as forensic phenotyping, it is achieved using single nucleotide polymorphism. Single nucleotide polymorphism have a lower mutation rate and likely to become fixed in a population. When working on phenotypes, they mainly focus on pigmentation, although researchers have developed an SNP typing involving mutations in the human melanocortin. DNA profile interpretation The primary purpose of this process is for forensic DNA profiling is to obtain samples from the DNA fingerprint and compare with profiles from the crime scene and profiles in the database. Modern profiling includes the statistical knowing that two people will share the same profile by how a genotype is common within the population. Benefits of DNA testing Genealogical DNA testing has become popular nowadays because of the need for research. Primary aim of the testing is for a forensic scientist to get evidence for criminal investigation, to solve parenting issues determine the relatives who might have filed a claim. Ways to package biological evidence When collecting natural evidences it is important to be recorded and photographed on sketches. The person collecting the evidence should remember to collect the latex gloves to avoid disrupting the findings. Any clothing of victims or suspects that have blood should be collected and not left. The use of airtight containers and plastics is not advisable when packaging the biological evidence because when moisture accumulates it contributes to DNA growth. It will, therefore, destroy the bacteria and fungi. Dried blood evidence can be obtained by using a sterile cotton swab that is moist with purified water before being placed in a swab box. All the evidence should refrigerate till the time it is taken to the laboratory. Collection methods vary with the kind of proof and the substrate. Therefore, it is always preferred to collect the evidence in its original state. In a situation where the evidence is delicate or can quickly loose the entire object should be unruffled and wrapped if the size permit. Some laboratories endorse the idea of the collection of clean samples or spotless portions of the material for biological evidence. It can use these to troubleshoot impurity, polymerase chain reaction inhibition or intrusion with fluorescence. Procedure for evidence collection Cuttings are collected by removing a section of the item with the stain using a clean cutting device. Wet absorption process is a sterile swab in which threads are slightly moistened with sterile distilled water. The stain should concentrate in a localized portion of the swab especially on the tip. It is concentrated into the stain and allowed to dry up in which both swabs are retained and submitted for analysis. The last method for collecting fluids is lifting with tape. The procedure is for dried blood stains on a non-absorbent surface; the tape is put over the stain, lifted and transferred to the adhesive side of the tape. Collection of hair and fiber uses three procedures; visual selection, tape lifting and vacuuming method. Visual collection involves using the naked eyes to see with the use of forceps and trace paper. Vacuuming method is where the suspected sample are vacuumed up and caught in a filtered trapped attached to the vacuum.The individuals should give reference sample especially those who were in the crime scene where DNA evidence is evident. Elimination or comparative analysis helps in the use of the reference sample. There are two procedures when sampling reference samples i.e. buccal swab and liquid blood sample. The oral swab procedure uses a sterile swab which rubs against the cheeks of the individual mouth to collect the epithelial cells for analysis. The fluid blood sample method uses purple top vacuum tubes that contain the preservative ethylenediamine tetra-acetic acid. When packaging evidence it has to pass through a drier to avoid it from degrading. Some prefer to package it in the paper but then if it is thoroughly dry it and keep in a plastic container. Liquid samples like water from a bowl, blood samples should have a proper documentation and then packaging is done in a pure glass, plastic containers and refrigerated as soon as possible. References Richard, S. (2007). Introduction to forensic science. Prentice Hall. Christine, H., &Kaen, M. (2012). Criminal investigation. Engage learning publishers. Charles, S,.& Neil, C. (2011).Criminal investigation.McGraw-Hill publishers. John, M. (2008).Advanced topics in forensic DNA typing: Interpretation.Academic press. Stuart, H., & Jon, J. (2007). Forensic science: An introduction to scientific and investigative techniques. CRC press. Read More