Free A Brief History of DNA and its Impact on the Field of Criminal Investigation Essay Sample
Deoxyribonucleic acid is one of two types of nucleic acids, providing storage, transmission from generation to generation and implementation of a genetic program of development and functioning of living organisms.DNA is a complex molecule that contains all of the information necessary to build and maintain an organism. The main role of DNA in cells is a long-term storage of information about the structure of RNA and proteins. Deciphering of the DNA structure was one of the turning points in the history of biology.
History of DNA
In the scientific literature devoted to the study of DNA, one can find the names of James Watson and Francis Crick, as the scientists who created a model of the structure of the DNA molecule in 1953. However, the molecule itself had been discovered much earlier. The name of a pioneer is not mentioned in every textbook, reference book or encyclopedia.
The discovery of deoxyribonucleic acid is attributed to a young Swiss physician Johann Friedrich Miescher. In 1869, while working in Germany, he studied a chemical composition of animal cells. He chose leukocyte cells as an object of his research.
The scientist extracted leukocytes from the purulent material as there were a lot of white blood cells in the pus that were performing a protective function in the body and destroying microbes.
Miescher washed leukocytes off the cloth bandages taken of the fresh festering wounds. Then, he separated protein molecules from the washed cells. During the investigations, he managed to establish that leukocytes contained more unexplored substances except proteins. It extracted as the precipitations of filamentary or flake structure while creating an acidic environment. Investigating leukocyte under a microscope, Miescher found that during the process described above, only nucleic remained. On this basis, he concluded that the nuclei of cells contained an unknown substance; and he called it nuclei, from the Latin word nucleus.
During a more detailed study, Miescher has developed a whole system of isolation and purification of nucleic. The separated compounds were not fat compounds and had not the protein nature as during the processing with enzymes, they were not undergoing any changes.
A chemical analysis, in those days, was imperfect, imprecise and time-consuming. Slowly but correctly, the scientist carried out the analysis and determined that the nucleic consisted of carbon, hydrogen, oxygen, and phosphorus. Phosphorous organic compounds were virtually unknown in those days, so Miescher concluded that he has discovered an unknown to science class of compounds that were contained within the cells.
The scientist wanted to publish an article about his discovery in the journal of his teacher Felix Hoppe Seyler who was one of the founders of biochemistry. However, before printing the material, Felix Hoppe Seyler decided to check his data in his laboratory. This study had taken the whole year; and only in 1871, in one of the issues, the work of Miescher was published. It was accompanied with two articles of Hoppe Seyler and his associate, confirming the data about the composition and properties of nucleic.
After returning to Switzerland, Miescher accepted an offer to become a Head of the Department of Physiology at the University of Basel. There, he continued his research. At the new location, the scientist used to experience the more enjoyable, and not less rich, nucleic material, i.e. salmon milt (it is still used for the same purpose). On the banks of the Rhine, rich in salmon, flowing through Basel, he had no shortage of the studied material.
In 1874, Miescher published an article in which he argued that the nucleic found in salmon milt is clearly associated with a process of fertilization. However, he did not associate it with heredity. The scientist considered his discovery so simple and uniform, and he even could not imagine that this compound could store all the different hereditary characteristics of living organisms.
Existing at that time methods of a biochemical analysis did not allow detecting the significant differences between the human nuclei and salmon nuclei. Moreover to recognize such a complex structure, it is still not fully recognized today.
The last decades of the XIX century were exciting in biology. Experimental findings and hypotheses that explained the new facts appeared at that time with the great intensity.
The existing of a new type of substances in the nuclei of cells has caused the battle of ideas about their biological role. In this fight, the correct understanding of nucleic as a carrier of hereditary properties of living prevailed for some time. However, in the further development of the biology, this important idea was abandoned. It took half a century so that this idea has revived again, fully confirmed. It has caused a revolution in the biological science, which is observed in our time. This idea has given birth to a new molecular approach for the important biological phenomena.
As a result of a chemical research, the first theory of the structure of nucleic acids was created. It was found that DNA and RNA are high molecular substances. It was a period during which biologists, without giving any clear report about the biological role of nucleic acids, accumulated the information about their distribution in various types of plant and animal tissues, bacteria and viruses, and in some unicellular organisms. It was shown that the DNA was not only in the nucleus of an animal cell, but also widely distributed in nucleus of a plant cell.
In 1936, a young Soviet scientist Belozersky, who later became an academician, first preoperatively, isolated DNA in a purified form from plant material.
The year of 1953, as it was mentioned at the very beginning of the paper, was a turning point in the development of science.
The sentence This structure has novel features which are of considerable biological interest" may be one of science's most famous understatements. It appeared in April 1953 in the scientific paper where James Watson and Francis Crick presented the structure of the DNA-helix, the molecule that carried genetic information from one generation to the other.
DNA is present in all the chromosomes of cells and plays a crucial role. It carries genetic information, so it is more often called a genetic map of the body. DNA molecules consist of two long chains of atoms forming different compounds (adenine, cytosine, guanine and thymine). They interlock with each other, forming a structure, known as a double helix. All information about life and all its physical characteristics (height, hair color, complexion, and etc.) is written in DNA and defined by the structure of the molecule. For such a sensational discovery, Watson and Crick with one more biologist were awarded with the Nobel Prize 1962 in Physiology and Medicine.
Thus, the period of the end of the XX century the beginning of the XXI was marked by an outstanding discovery in biology, i.e. the human genome. People entered into the genomic era that legally let 0justify innocent people, reliably establish paternity and reinstate the legitimate heirs. However, at the same time, the availability of this knowledge to others and law enforcement makes a citizen be a hostage of potentially legal problems.
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The Impact of DNA on the Field of Criminal Investigation
In order to understand better what portions of genes are and how they can be used for identification purposes, it is necessary to consider some important information about the human genotype and the structure of the DNA molecule.
According to recent figures, a human genotype consists of 4000 genes, their 70 associations and 7 main blocks. Each gene (there are 30000 100000 genes) is located in chromosome pairs. One half of the proceeds is descended from a father, the other - from a mother; and both transmit the corresponding inherited characteristics. Gene inheritance is like a kaleidoscope in a principle: in which image numerous components that carry hereditary traits will develop. The number of variants is innumerable. I It is important not only the quality of the participating associations and blocks, but also their level of compatibility.
A genome of an individual is a set of genes, i.e. a complete set of instructions for the creation of human beings. Encoded in the genome instructions determine the external symptoms of a person (height, complexion, face shape, eye shape, hair color, and etc.), as well as intelligence, susceptibility to disease, and life expectancy. A genetic passport of human comprises 3 billion marks; and each single gene comprises from 10 to 150 thousand code letters.
DNA is a huge molecule located in the nuclei of human cells in the form of 46 individual strands, each of which is rolled into a ball, called a chromosome. DNA is folded into a double helix, like a twisted rope ladder, the sides of which are composed of sugars and phosphates. They are tightly connected with a "beam", which are called base pairs as they consist of two chemical compounds of nitrogen bases.
Each of the bases represents a letter in the genetic code. Along DNA molecules, sequences of bases are arranged and repeated several times. These sequences are located in the so-called nitrone (parts of the genes that do not carry useful information). They are composed of nucleotides, which are repeated 3 to 30 times and distributed over the entire length of DNA. A person can have the same sequence of nucleotides repeated 5 times in the same place, then 15 times in the other place, and then 25 times in the third. Another person can have sequences that would consist of a different number of nucleotides and occupy other places of DNA.
A creator of the genomic expertise, English biologist A. Jeffries in 1983 revealed the presence of such places of sequences in DNA molecules that were specific to each individual. He developed the practical utilization of this phenomenon in criminology. The scientist has proved that all people have a different number of such places, which are called a mini-satellite of the DNA. The ratio of their lengths is also different (some people have a lot of long and small amount of such mini satellites and vice versa). Finally, each sequence has a different number of nucleotides. Therefore, there is more than enough amount of genetic elements in order to create a method of human identification in the structure of its DNA.
Thus, DNA has a significant impact on the field of criminal investigation. There are several reasons why a DNA molecule is so attractive for its use in criminal investigation:
- The uniqueness of the individual DNA. Everyone in the world is different genetically (except for identical twins, which are essentially clones).
- Genetic constancy of the body. The genetic information, unlike the composition of proteins or fats, does not change during the lifetime, and also depends on the type of cells from which DNA has been isolated.
- Sensitivity of the method. For modern methods of a DNA analysis is sufficient even few drops of blood or a saliva sample, or semen stains, found in the area that is in 10 times smaller than a pinhead, or DNA from smoked cigarettes.
- The relative stability of DNA molecules. Unlike proteins that have unstable structures, the DNA molecule has a high resistance to environmental influences. This property of DNA is valuable in criminology because it allows the one to identify criminals even after a very long time, or if human remains cannot be identified by any other means (for example, in case of aircraft accidents).
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There are a lot of stories about the successful use of DNA molecules in criminal investigation. According to Advancing Justice through DNA Technology.
In 1999, New York authorities linked a man through DNA evidence to at least 22 sexual assaults and robberies that had terrorized the city. In 2002, authorities in Philadelphia, Pennsylvania, and Fort Collins, Colorado, used DNA evidence to link and solve a series of crimes (rapes and a murder) perpetrated by the same individual. In the 2001 Green River killings, DNA evidence provided a major breakthrough in a series of crimes that had remained unsolved for years despite a large law enforcement task force and a $15 million investigation.
There are some methods of determination of DNA profiling. Currently, such method as a full reading of the human genome is available. This method would give a definite answer about the identity of samples. However, the method is too expensive for its everyday use in practice. However, there is no need in identification of full genome. It is enough to compare some places of the genome. For the comparison of the samples of genomes, STR-loci are used. According to Butler, 2006, The core loci currently employed in human identity testing have demonstrated their usefulness in aiding the resolution of numerous criminal and parentage testing cases over the past dozen years.
The identification accuracy depends on how often the detections in samples of variants and combinations are met among the population. If there the detection is very popular among the population (is met among the half of the population), its value is not identifiable. If the detection is rare, then the identification can be ambiguous. Therefore, it is necessary to know the frequency of occurrence of variants used for identification of a DNA profile for the DNA identification in the medical and forensic examination.
Proper identification is carried out in two stages. At the first stage, the DNA profiles of biological samples collected at the crime scene, a terrorist attack or disaster are identified in the laboratory. This profile can be compared with the DNA profile of the suspected person (if he/she is cached) or with samples from the databases that store DNA profiles previously convicted or suspected of committing crime entities.
If these profiles do not match, the answer is negative (an offender is not found). If the profiles match, then it is necessary to estimate the probability that this coincidence is not accidental.
Suddenly there are one or more persons who have the same DNA profile characteristics, and, in fact, which are not suspected in crime. Thus, it is necessary to evaluate the frequency of occurrence of the particular profile in the population of a region or a group of people, which may include a suspected person.
In order to estimate the probability of identification, the databases of frequency of occurrence of STR- variants used for identification in different populations are created.
Thus, there are two types of databases of DNA profiles used in forensics. The first one is a database containing the DNA profiles of persons identified in the investigation of crimes. They are used to find matches with the DNA profile from a crime scene, as in the number of types of crime. The relapses are of a significant portion (80%).
The second type is the population database characterizing DNA profiles of people of different countries, geographic regions, and ethnic-territorial groups. These databases, as already stated, are used to assess the likelihood that any of individuals may have the same genetic characteristics.
DNA is not only used for the identification of criminals, but also for such a purpose as paternity determination.
The reasons for a DNA analysis for paternity determination are met in the peoples life very often. Reliably determining the degree of a relationship is necessary to resolve legal problems, family reunion, determining the tissue compatibility, and just for the confidence that a man brings up his child. Recently, this analysis has been difficult and expensive; and the degree of reliability was doubtful. Modern techniques of genetic studies allow responding to any questions according to the issues mentioned above accurately and quickly.
They are based on the fact that the DNA of each person is unique, and one half of it is derived from a biological father, and the other - from a mother. In compared pairs mother-child or father child, the studied fragments completely match in the case of gentility.
Tests are conducted with any biological sample containing DNA. It can be blood and cheek epithelial cells, and such complex biological materials as nails, hair or bone.
The result of the analysis is independent of the type of the biological material, the presence of a human disease, and age. The result is the same in either case.
According to El-Alfy & El-Hafez, he paternity testing is based on matches of the alleles at the 15 STR loci between the child and the mother and the alleged father. For motherless cases or duo cases, matches of the alleles of the STR loci were performed between the child and the alleged father.
In order to determine the paternity, a molecular genetic study is conducted (the comparison of high-polymer fragments of DNA of the child and the alleged father)
In order to prove the biological relationship confidently, it is enough of 99.9 % of the precision. In this case, the scientific world used the phrase parenthood practically proven. This level of reliability is much easier to achieve if not only the father and the child are tested, but the birth mother as well. Therefore, in the case of an examination designed by the court, the biological material for a research is taken from all members of the family (the mother, the father and the child).
In order to exclude paternity, it is necessary to identify at least three differences in the DNA fragments subjected to the study.
The DNA analysis can detect a wide variety of family ties, but most applications still account for paternity.
Moreover, men often asked first to study privately in order not to offend a wife or beloved ones with suspicions.
In the case of confirmation of such suspicions, they turn to the courts for an official investigation. It helps in solving a lot of legal issues related to child support, inheritance, and etc. However, it happens that such an analysis is required by the biological mother in order to solve the same problems in her favor, or when she can not clearly indicate who the father of her child is. At different stages of pregnancy, various materials are taken for the analysis (the villi of the chorion, amniotic fluid, and umbilical cord blood).
The need to conduct test for DNA paternity determination during pregnancy occurs in a variety of situations. For instance, the alleged father is sure of his sterility or suspects his wife of infidelity. In this case, a similar study helps to keep the family and father to the unborn baby.
Analyzing all the information mentioned above, it becomes clear that DNA has a huge and significant impact on the field of the criminal investigation. With the help of the DNA analysis, officers of the law can justify innocent people and quickly catch criminals. It also reliably establishes paternity and reinstates the legitimate heirs. Thus, it is obviously that the influence of DNA is only positive.