Criminal DNA Testing

DNA or Deoxyribonucleic acid refers to the genetic material in the cells of a human body. Every human being receives half of the DNA from the biological mother and the other half from the biological father. With advances in technology, DNA evidence has become a vital forensic technique to identify criminals when biological tissues are found at the crime scene. A single hair root, saliva, blood or semen can help in the identification and conviction of criminals. Sweaty shirts, fingernail clippings, urine, chewed gums, used tissues and licked stamps can also be used for testing. DNA can be used to make the portrait of a probable suspect. DNA evidence is also useful in determining skin color and eye color. DNA fingerprinting, which is also known as genetic fingerprinting, is a very important tool in the identification of criminals.

The majority of DNA of one person may match the DNA of another person. This makes the process of differentiation between two people extremely difficult. Microsatellite is a particular type of DNA sequence that simplifies the process of identification. Microsatellites are small pieces of DNA that occur repeatedly in a person's DNA. They tend to vary in a particular area and their comparison helps in identifying a person quite effortlessly.

It is almost impossible to eliminate all the physical traces of a person's presence at a place of crime. A single cell is sufficient to identify victims even in situations where the body is completely destroyed. DNA fingerprinting is not accurate as a regular fingerprinting process but it does provide some clue to begin an investigation.

In post conviction cases, DNA testing also helps attorneys prove a client's innocence. In cases where the biological evidence was collected but DNA testing was not carried out, the evidence can be subjected to DNA testing to absolve the client. In cases where biological evidence was never collected or biological evidence was destroyed, post conviction on the grounds of DNA testing is not possible.

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What Is Gel Electrophoresis?

One of the many DNA tests that it is important to comprehend to get a better understanding of laboratory DNA testing is gel electrophoresis. This test is one used by anyone that is doing DNA testing because of its ability to differentiate between the different fragments of the DNA, thus it is suitable for most comparisons and family relationship testing processed. These fragments of DNA, as found as evidenced in murder and rape criminal cases, can help a forensic scientist try and determine who, and more importantly if the accused, is guilty of the crime in question. However, it is also used for many other scientific purposes, and the principle that make it work are relatively simple to understand in laymen's terms.

Using an endonuclease which is an enzyme, the scientist can fragment the DNA down to its three base pairs, commonly called codons. By doing this, they take a very large DNA sample and they make it much smaller and much easier to use. By making it smaller and easier to use, the scientist can then run the gel electrophoresis and observe the different molecular weights. They then try to determine what amino acids are present and by pushing the genetic code through the gel, scientists can begin to differentiate between the two.

Once they have created the fragments of DNA, the next step is to run it through the gel. The gel is usually a cross linked polymer which is chosen based on the weight and composition of the sample they are analyzing. When scientists are separating proteins or small nucleic acids (such as DNA), the gel is made up of different concentrations of acrylamide and a cross-linker.

The scientist then makes small wells in the gel so that they can insert microliters of the sample in them. They put the gel into a container that allows for an electrical current to go through it. By putting the charge through the electrophoresis container, they are allowing the molecules to move away from the negative anode and towards the anode. They move, usually, based on their molecular weight. Different base pairs weigh different amounts and placement of the different codons on the gel determines, potentially, what the different components are.

The next step in this particular DNA test is to stain the gel. By using ethidium bromide, testers can make the gel readable and observable. They can compare known gels to this unknown and try and determine what the different base pairs are in this sample. Therefore, regardless of what the use of the electrophoresis is, it can help the scientist identify different molecular components found in an unknown sample.

Some other branches of science that this tool is used for are forensics, molecular biology, genetics, microbiology and biochemistry, in which this form of gel testing can be used to draw parallels and distinctions. However, many other branches of both biology and chemistry use this test an effective way to examine different substances and to compare where potentially relevant similarities exist.

Kevin Camilleri writes articles for dna paternity test. Other articles written by the author related to paternity testing, home paternity test and paternity test kit can be found on the net.

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