The Use of Biochemistry in Forensic Science - Literature review Example

Running Header: The Use of Biochemistry in Forensic Science Student’s Name: Instructor’s Name: Course Code & Name: Date of Submission: The Use of Biochemistry in Forensic Science Introduction According to Templin (2001, p.1) biochemistry deals with matter molecules ‘biomolecules’ which make up living organisms. Nuclei acids, lipids, carbohydrate and proteins are vital to biochemistry. Biochemistry is also associated with structure of the biomolecules function. Biochemistry has been utilized to bridge between biology and chemistry; it’s also a major section of science of its own. It has been also used as a method to study almost all problems associated with biology at level of molecules. Understanding biochemistry helps in giving the critical foundation for appreciating every field of life sciences, including genetics and microbiology. DNA is a nuclei acid that encodes the information of genetic for establishment of traits of an organism, such as blood type and eye colour. There has been a fast growing science that has positively affected advances such as project in human genetics. Forensic science has used techniques from many disciplines of science including chemical, physical and visual analysis. Siegel (2009, p. 5) suggests that forensic science can be viewed as means of applying science to matters of public but it can also be used to refer to techniques of applied science to justice system matters. Civil or criminal issues have been handled in justice systems using forensic science. In history of forensic science, Chinese were the first to utilize this knowledge in process of identification. They utilized fingerprints to investigate the owner of property such as pottery but the process had no formal process of classification. In later years, many scientists including Marcello Malphighi identified the fingerprints presence and they exhibited unique characteristics, but did not develop any relationship to identification of a person. John Purkinji was the first person to discover fingerprints and he was a professor of anatomy. In 1900, Lansteiner Karl made a major development in the blood analysis where he found out that there are 4 human blood types. In 1984, Jeffries utilized a method known as DNA fingerprinting to handle a double murder case in England, the first case to be solved by analysis of DNA. Biochemical knowledge such as DNA finger printing is critical to science of forensic. DNA Biochemistry Understanding of DNA biochemistry is fundamental to forensic science. The life basic unit is cell, which is the central unit producing energy, raw materials and removing waste. It is essential to sustain life. Enzymes are made of many different proteins and are essential for survival of cell functioning. A person is approximately made of 100 trillion cells, all which come from single cell. Every cell has similar genetic programming. In the cell nuclei is chemical substance called DNA that has the information code for replicating cell and developing the required enzymes. Templin (2001, p.1) indicates that DNA is usually referred to as nuclear DNA since it is found in nucleus. DNA or Deoxyribonucleic acid is also known as our blueprint of genetics since it preserves the information required to pass down as genetic attributes to generation of the future. Found in every body cell (excluding red blood cells, which lack nuclei), DNA gives ‘a program of computer’ that establishes many attributes and physical features. DNA has two major functions; carrying instructions on how to build proteins and producing copy of itself in order to divide and transport on the same information. Information stored in structures of DNA is transferred from one generation to another with half of DNA information of a person obtained from their father and the other half from the mother. Nucleic acids and DNA are made of nucleotide units that are composed of 3 parts: phosphate, sugar and nucleobase. Butler (2005, p.18) indicates that the base or nucleobase gives disparity in every nucleotide unit while sugar and phosphate portions make the backbone of the molecule of DNA. The alphabets of DNA are made of four characters representing the 4 bases: A (adenine), C (cytosine), G (guanine) and T (thymine) Figure 1.Components of nucleic acid Components of nucleic acid (Butler 2005, p. 18) The different combinations of these 4 letters, referred to as base or nucleotides produce the varied biological differences in human beings and every living organism. It is approximated that human has 3 billion positions of nucleotides in their genomic DNA. With possibilities of 4 (G,C,T and A) at each position combinations of trillion probabilities are possible. Champe, Harvey and Ferrier (2005, p. 414) indicate that DNA information content is encoded in sequence (order) of the nucleobase just the way computer store binary data in a string of zeros or ones. Directionality is given when listing a sequence of DNA by assigning the 3-end and the 5-end. This scheme of numbering is from the DNA chemical structure and refers to the carbon atoms position in the sugar ring which is backbone of DNA structure (figure 1). A sequence is usually read and written from 5 to 3 unless informed otherwise. DNA polymerases, the enzymes copying DNA, only write sequence of DNA information from 5 to 3 i.e. from left to right. DNA in its natural state is usually made of 2 strands that are connected together through a procedure known as hybridization. Every nucleotide pairs up with it complementary base through bond of hydrogen that is made between bases. The rules of pairing are such that cytosine can only hybridize to guanine and adenine can only hybridize to thymine (figure 2) Figure 2. Base pairing of DNA strands Base pairing of DNA strands (Butler 2005, p. 19) There 2 bonds of hydrogen between base pair the adenine-thymine and 3 bonds of hydrogen between the base pair of guanine-cytosine. AT base pairs are weaker compared to GC base pairs. The 2 DNA strands make a double helix because of base- pairing phenomenon (figure 2). The two DNA strands are anti-parallel i.e. one strand is in the 5 to 3 orientation and the rest lines of strands lines up in 3 to 5 path in relation to the initial strand. Campbell and Farrell (2009) suggests that understanding one DNA strand sequence, its sequence of complement can simply be established regarding to the rules of base pairing of G with C and A with T. These combinations are also known as Watson-Crick base pairs for Francis Crick and James Watson who revealed the relationship of structures in 1953. Hybridization of 2 strands is a DNA fundamental property. Nevertheless, the bonds of hydrogen holding the 2 strands of DNA together by means of pairing base may be destroyed by chemical treatment or elevated temperature by a process referred to as denaturation. This is important especially when handling and storing forensic samples. Double stranded DNA can be denatured by heating to almost temperatures of boiling point. Double helix DNA can be denatured by rendering it to denaturants chemicals such as formamide or urea or low strength ionic salt solution. The destabilisation of DNA is as a result of formation of hydrogen bonds with the nucleotides and resisting their contact with complementary DNA strand. The process of denaturation is irreversible. If DNA double-strand piece is heated up, it segregates into 2 mono strands. As the sample of DNA loss heat, the mono DNA strands will search their sequence of complementary and anneal or rehybridize one another. The process of the 2 complementary strands of DNA combining together is known as reannealing or renaturation. Butler (2005, p.20) suggests that there exist about 3 billion base pairs in one copy of the genome of human. Getting a full catalog of human genes was the main object of the Human Genome Project, which published a most recent reference of human genome sequence in 2003 April. This information is predicted to be helpful in forensic and medical science. In the cells of human, DNA located in cell nucleus is categorized into chromosomes, which are highly packed packets of DNA and proteins for protection known as histones. The genomes of human are of 22 matched pairs of autosomal chromosomes and 2 chromosomes determining sex. Cells of a normal human have 23 pairs of chromosomes or 46 varying chromosomes. Males are assigned XY since they have a single copy of chromosome of Y and a single X chromosome. Homologous is the term used to describe pairs of chromosomes since they equal size and have similar genetic structure. Every copy is located at the same position (locus) on every chromosome of homologous pair. 1 chromosome in every pair is inherited from person’s father and the other from mother. Champe, Harvey and Ferrier (2005, p. 393) have stated that the possibilities of alternative for genetic or gene locus are also known as alleles. If 2 alleles at a genetic locus on chromosomes for homologous are identical at a certain locus they are referred as homozygous and if the alleles are varying, they are referred to as heterozygous. Differences that are detectable in alleles at corresponding loci are vital to human identification test in forensic science. A DNA profile is the mishmash of genotypes acquired for multiple loci. DNA profiling or typing is a procedure of establishing the presence of genotype at particular positions along the molecule of DNA. In forensic tests, multiple loci are usually investigated in person identification test to lower the occurrence of a random match between unrelated persons. DNA Markers If a marker falls within a gene or is part of the gene, the name of the gene is utilized in the designation. Illustration; where the short tandem repeat (STR) marker TH01 is from the human tyrosine hydroxylase gene situated on chromosome 11. The 01 section of TH01 exist because the repeat region in question is situated in ‘1’ of the tyrosine hydroxide gene.HUM prefix is utilized to indicate that it is obtained from genome of a human. Therefore, STR locus TH01 will be indicated as HUMTH01. A staining method is a technique for staining chromosomes to acquire a banding pattern by using Giemsa dye mixture that give G-bands. G-banding is paramount in chromosomes since it helps in establishing where specific DNA gene or sequence is situated in relation to other DNA markers. The chromosomes variations in banding pattern and size allow the 24 chromosomes to be differentiated from one another by analysis referred to as karotype in forensic science. DNA Polymorphisms Variations of DNA are shown in form of varying allele, or varying possibilities at a specific locus. According to Butler (2005, 26), two types of variation exist at the level of DNA: length polymorphisms and sequence polymorphism. Multiple loci or markers are examined in DNA typing. The more Marker of DNA are compared and examined, the higher the possibility that two unrelated individuals will have varying genotypes. Additional, every piece of matching information complements to the confidence in bonding two matching DNA profiles from the same person. Product rule is applied where every locus is inherited free of the other loci and calculation of a profile frequency of DNA are obtained by multiplying every separate genotype frequency together. In forensic tests, it infeasible to examine the overall DNA sequence of a person because of cost and time. However, multiple separate locations are assessed. The variability acquired in these locations is utilized to exclude or include sample in forensic test. DNA searches can be reduced by comparing points of multiple data in an analogue method like one used to deliver mails in U.S postal services. The whole U.S has above 290 million people but they use name, street number, street, city, state and zip code to deliver mail to a specific individual. The same situation is applied, the inclusion of more and more data from DNA markers is utilized to slim a search down to a single person. If marker 3, marker2, marker 1and so on compares to DNA profile between a suspect and evidence of crime of scene, a person will be more sure that the 2 DNA types emanates from the one source. In forensic science, the probability increases with each match of the mark. The use of short tandem repeat (STR) DNA markers for individual testing has gained popularity in forensic science because it can be easily automated. It also includes sensitive fluorescent detection, which allows investigators to collect data fast from the markers. STRs are more discriminating between closely related and unrelated persons when examining sites on multiple chromosomes. Separate alleles allow easier interpretation of results and comparison by use of DNA database that is computerized. The polymerase Chain Reaction (PCR) Butler (2005, p.68) reported that PCR is mostly carried out with volume of a sample ranging between 5ŲL to 100 ŲL. There is a problem of evaporation because of the minute volumes involved and exact pippetting of the components of the reaction can be a nightmare. At the same time, huge volumes of solution lead to the challenge of thermal equilibrium for the reaction mixture since it lengthen time for change of internal temperature to be transferred to the large solution center than a minute one. Thus, majority of PCR molecular biology protocols are within 20-25 ŲL. In the recent years, PCR has been made simple by the reagent kits availability that permit a laboratory for forensic DNA to easily add a template of DNA to pre-prepared mixture of PCR having all constituents for the enhancing reaction. APCR reaction is made through mixing of various constituents and later adding distilled water to acquire the desire concentration and volume of every constituent. The vital components of PCR reaction are 2 primers, which include small DNA sequence that flank the area to be copied. A primer helps to establish the section of DNA template to be copied. The other constituent of reaction of PCP contain a template DNA that will be copied, making blocks consisting of each of the 4 nucleotides, and polymerase of DNA that puts in blocks of building in an appropriate order basing on sequence of DNA template. DNA extraction and Sample collection The process of DNA extraction and sample handling requires knowledge of biochemistry in order to prevent compromise in an evidence.The sample is collected and DNA isolation is done before a test of DNA is carried out. After extraction the sample required to be in proper format for further investigations. Siegel (2007, p.35) warns that if the samples are mishandled in the beginning of the investigation, it will be hard to compensate this in data interpretation or final analytical steps. DNA exist in each cell nucleus and this means that it also exist in the biological materials that are found in scenes of crimes. Forensic scientists have been able to isolate and analyze DNA from wide range of biological materials. Presence of polymerase chain reaction (PCR) has widened the limits of possible DNA samples that can be properly evaluated since majority of copies are obtained from markers’ DNA to be assessed. The majority of substances analyzed in forensic laboratories are semen stains and blood stains or semen and blood. These biological evidences can be utilized to exclude or associate a person in committing a crime. DNA transfer from one person to another person or an object can be utilized to connect an individual to the scene of crime. Biological material sources utilized for PCR- based DNA typing include: blood and blood stains, semen and semen stains, bones, teeth, hair with root, hair shaft, urine, feces, debris from finger nails, muscle tissues, cigarette butts, postage stamp, envelop sealing flaps, dandruff, fingerprints and other personal items. Transfer that is direct includes: i. DNA deposited by suspect on the body or clothing of the victim. ii. DNA deposited by suspect on an object. iii. DNA deposited by suspect at a location. iv. DNA deposited by the victim on the clothing or body of the suspect. v. DNA deposited by the victim on the object. vi. DNA deposited by the victim at a location. vii. DNA deposited by the witness on the victim or suspect. viii. DNA deposited by the witness on a location or an object Illustrations Between 1983 and 1986 2 girls were assaulted sexually and later barbarically murdered. Both girls were murder in Narborough in Leicestershire, England in the same circumstances, leading investigators to believe that both crimes were committed by the same person. To find the killer, a huge screen to take blood samples from every adult man ensued where over 4000 men were tested but later the killer was found and sentenced to life imprisonment. According to Joseph (1989), this was first case to apply genetic fingerprinting forensic DNA typing. In 1998, Monica Lewinsky claimed that she had a sexual relationship with the then president, Bill Clinton. Since the allegations were emphatic, the investigation ensued. The dress belonging to Monica was taken to FBI forensic laboratory for analysis. The unknown semen was identified on the dress and it was analyzed. Woodward (1999) indicates that the reference blood sample was taken from President Clinton on 3 August 1998. The RFLP markers were utilized to match the semen stain and the president blood sample but concurrently another analysis using STR typing methods was being carried out. High molecular weight DNA from the president Clinton blood and semen stain was digested with enzyme of restriction. At all seven RFLP loci analyzed, a seven probe match was attained. The results of the DNA analysis were reported that 7 genetic loci showed that president blood sample and the semen stain matched to a certain degree of scientific certainty. President found himself in a tight corner following the previous denial. Conclusion It is clear that biochemistry plays a major role in forensic science because the process is highly dependant on the biomolecule analysis. Liverpool John Moores University (2009) has confirmed that DNA has been widely used by forensic sciences as the biomolecule of the living cells. The importance of DNA in forensic is based on the ability of Deoxyribonucleic acid to preserve the information on genetics and passing the same attributes from one generation to the other. The DNA information content is encoded in sequence (order) of the nucleobase just the way computer store binary data in a string of zeros or ones. The connection between 2 strands in DNA occurs through a process known as hybridization. Forensic sample can be destroyed by chemical treatment or elevated temperature by a process referred to as denaturation. Multiple loci or markers are examined in DNA typing. The more Marker of DNA are compared and examined, the higher the possibility that two unrelated individuals will have varying genotypes. SRT DNA markers for the purpose of forensic science have gained popularity because there are easily automated. In PCR analysis, there is a problem of evaporation because of the minute volumes involved and exact pippetting of the components of the reaction. DNA exist in each cell nucleus which means that it exist in the biological materials that are found in scenes of crimes. DNA analysis utilized in forensic science has progressively become an effective and sensitive tool to help in exonerating the innocent and bringing the guilty to justice. Biochemistry used in forensic science can have a huge impact on the events of the world. References Butler, M 2005, Forensic DNA typing: biology, technology, and genetics of STR markers, Elsevier Academic Press, Burlington, MA. Campbell, K & Farrell, O 2009, Biochemistry, 6th edn, Thomas Brooks/Cole, Belmont. Champe, P, Harvey, R & Ferrier, D 2005, Biochemistry, Williams and Wilkins, Philadelphia. Liverpool John Moores University 2009, Biochemistry and forensic science, Liverpool John Moores University, Viewed 25 July 2010 . Joseph, W 1989, The blooding, New York: Bantam Books, Viewed 25 July 2010, . Siegel, J 2007, Forensic science: the basics, CRC Press, Boca Raton. Templin, J 2001, Biochemistry essentials, Research and Education Association, New Jersey. Woodward, B 1999, Shadow: five presidents and the legacy of Watergate, Simon and Schuster, New York. Appendices Figure 1.Components of nucleic acid Components of nucleic acid (Butler 2005, p. 18) Figure2. Base pairing of DNA strands Base pairing of DNA strands (Butler 2005, p. 19) Read More